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< title > Boost.Mp11: A C++11 metaprogramming library< / title >
2017-06-07 00:02:25 +03:00
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< / style >
2017-03-14 22:57:07 +02:00
< / head >
2017-06-07 00:02:25 +03:00
< body class = "article toc2 toc-left" >
< div id = "header" >
2017-06-10 03:44:31 +03:00
< h1 > Boost.Mp11: A C++11 metaprogramming library< / h1 >
2017-06-07 00:02:25 +03:00
< div class = "details" >
< span id = "author" class = "author" > Peter Dimov< / span > < br >
< / div >
< div id = "toc" class = "toc2" >
< div id = "toctitle" > Table of Contents< / div >
< ul class = "sectlevel1" >
< li > < a href = "#overview" > Overview< / a > < / li >
< li > < a href = "#definitions" > Definitions< / a > < / li >
< li > < a href = "#examples" > Examples< / a >
< ul class = "sectlevel2" >
< li > < a href = "#generating_test_cases" > Generating Test Cases< / a > < / li >
2017-06-10 03:44:31 +03:00
< li > < a href = "#writing_common_type_specializations" > Writing common_type Specializations< / a > < / li >
< li > < a href = "#fixing_tuple_cat" > Fixing tuple_cat< / a > < / li >
2017-06-07 00:02:25 +03:00
< li > < a href = "#computing_return_types" > Computing Return Types< / a > < / li >
< / ul >
< / li >
< li > < a href = "#reference" > Reference< / a >
< ul class = "sectlevel2" >
< li > < a href = "#integral" > Integral Constants, < boost/mp11/integral.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_bool_b" > mp_bool< B> < / a > < / li >
< li > < a href = "#mp_true" > mp_true< / a > < / li >
< li > < a href = "#mp_false" > mp_false< / a > < / li >
< li > < a href = "#mp_to_bool_t" > mp_to_bool< T> < / a > < / li >
< li > < a href = "#mp_not_t" > mp_not< T> < / a > < / li >
< li > < a href = "#mp_int_i" > mp_int< I> < / a > < / li >
< li > < a href = "#mp_size_t_n" > mp_size_t< N> < / a > < / li >
< / ul >
< / li >
< li > < a href = "#list" > List Operations, < boost/mp11/list.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_list_t" > mp_list< T… ​ > < / a > < / li >
< li > < a href = "#mp_size_l" > mp_size< L> < / a > < / li >
< li > < a href = "#mp_empty_l" > mp_empty< L> < / a > < / li >
< li > < a href = "#mp_front_l" > mp_front< L> < / a > < / li >
< li > < a href = "#mp_pop_front_l" > mp_pop_front< L> < / a > < / li >
< li > < a href = "#mp_first_l" > mp_first< L> < / a > < / li >
< li > < a href = "#mp_rest_l" > mp_rest< L> < / a > < / li >
< li > < a href = "#mp_second_l" > mp_second< L> < / a > < / li >
< li > < a href = "#mp_third_l" > mp_third< L> < / a > < / li >
< li > < a href = "#mp_push_front_l_t" > mp_push_front< L, T… ​ > < / a > < / li >
< li > < a href = "#mp_push_back_l_t" > mp_push_back< L, T… ​ > < / a > < / li >
< li > < a href = "#mp_rename_l_y" > mp_rename< L, Y> < / a > < / li >
< li > < a href = "#mp_apply_f_l" > mp_apply< F, L> < / a > < / li >
< li > < a href = "#mp_apply_q_q_l" > mp_apply_q< Q, L> < / a > < / li >
< li > < a href = "#mp_append_l" > mp_append< L… ​ > < / a > < / li >
< li > < a href = "#mp_replace_front_l_t" > mp_replace_front< L, T> < / a > < / li >
< li > < a href = "#mp_replace_first_l_t" > mp_replace_first< L, T> < / a > < / li >
< li > < a href = "#mp_replace_second_l_t" > mp_replace_second< L, T> < / a > < / li >
< li > < a href = "#mp_replace_third_l_t" > mp_replace_third< L, T> < / a > < / li >
< / ul >
< / li >
< li > < a href = "#utility" > Utility Components, < boost/mp11/utility.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_identity_t" > mp_identity< T> < / a > < / li >
< li > < a href = "#mp_identity_t_t" > mp_identity_t< T> < / a > < / li >
< li > < a href = "#mp_inherit_t" > mp_inherit< T… ​ > < / a > < / li >
< li > < a href = "#mp_if_c_c_t_e" > mp_if_c< C, T, E… ​ > < / a > < / li >
< li > < a href = "#mp_if_c_t_e" > mp_if< C, T, E… ​ > < / a > < / li >
< li > < a href = "#mp_eval_if_c_c_t_f_u" > mp_eval_if_c< C, T, F, U… ​ > < / a > < / li >
< li > < a href = "#mp_eval_if_c_t_f_u" > mp_eval_if< C, T, F, U… ​ > < / a > < / li >
< li > < a href = "#mp_eval_if_q_c_t_q_u" > mp_eval_if_q< C, T, Q, U… ​ > < / a > < / li >
< li > < a href = "#mp_valid_f_t" > mp_valid< F, T… ​ > < / a > < / li >
< li > < a href = "#mp_defer_f_t" > mp_defer< F, T… ​ > < / a > < / li >
< li > < a href = "#mp_quote_f" > mp_quote< F> < / a > < / li >
< li > < a href = "#mp_invoke_q_t" > mp_invoke< Q, T… ​ > < / a > < / li >
< / ul >
< / li >
< li > < a href = "#algorithm" > Algorithms, < boost/mp11/algorithm.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_assign_l1_l2" > mp_assign< L1, L2> < / a > < / li >
< li > < a href = "#mp_clear_l" > mp_clear< L> < / a > < / li >
< li > < a href = "#mp_transform_f_l" > mp_transform< F, L… ​ > < / a > < / li >
< li > < a href = "#mp_transform_q_q_l" > mp_transform_q< Q, L… ​ > < / a > < / li >
< li > < a href = "#mp_transform_if_p_f_l" > mp_transform_if< P, F, L… ​ > < / a > < / li >
< li > < a href = "#mp_transform_if_q_qp_qf_l" > mp_transform_if_q< Qp, Qf, L… ​ > < / a > < / li >
< li > < a href = "#mp_fill_l_v" > mp_fill< L, V> < / a > < / li >
< li > < a href = "#mp_count_l_v" > mp_count< L, V> < / a > < / li >
< li > < a href = "#mp_count_if_l_p" > mp_count_if< L, P> < / a > < / li >
< li > < a href = "#mp_contains_l_v" > mp_contains< L, V> < / a > < / li >
< li > < a href = "#mp_repeat_c_l_n" > mp_repeat_c< L, N> < / a > < / li >
< li > < a href = "#mp_repeat_l_n" > mp_repeat< L, N> < / a > < / li >
< li > < a href = "#mp_product_f_l" > mp_product< F, L… ​ > < / a > < / li >
< li > < a href = "#mp_product_q_q_l" > mp_product_q< Q, L… ​ > < / a > < / li >
< li > < a href = "#mp_drop_c_l_n" > mp_drop_c< L, N> < / a > < / li >
< li > < a href = "#mp_drop_l_n" > mp_drop< L, N> < / a > < / li >
< li > < a href = "#mp_iota_c_n" > mp_iota_c< N> < / a > < / li >
< li > < a href = "#mp_iota_n" > mp_iota< N> < / a > < / li >
< li > < a href = "#mp_at_c_l_i" > mp_at_c< L, I> < / a > < / li >
< li > < a href = "#mp_at_l_i" > mp_at< L, I> < / a > < / li >
< li > < a href = "#mp_take_c_l_n" > mp_take_c< L, N> < / a > < / li >
< li > < a href = "#mp_take_l_n" > mp_take< L, N> < / a > < / li >
< li > < a href = "#mp_insert_c_l_i_t" > mp_insert_c< L, I, T… ​ > < / a > < / li >
< li > < a href = "#mp_insert_l_i_t" > mp_insert< L, I, T… ​ > < / a > < / li >
< li > < a href = "#mp_erase_c_l_i_j" > mp_erase_c< L, I, J> < / a > < / li >
< li > < a href = "#mp_erase_l_i_j" > mp_erase< L, I, J> < / a > < / li >
< li > < a href = "#mp_replace_l_v_w" > mp_replace< L, V, W> < / a > < / li >
< li > < a href = "#mp_replace_if_l_p_w" > mp_replace_if< L, P, W> < / a > < / li >
< li > < a href = "#mp_replace_at_c_l_i_w" > mp_replace_at_c< L, I, W> < / a > < / li >
< li > < a href = "#mp_replace_at_l_i_w" > mp_replace_at< L, I, W> < / a > < / li >
< li > < a href = "#mp_copy_if_l_p" > mp_copy_if< L, P> < / a > < / li >
< li > < a href = "#mp_remove_l_v" > mp_remove< L, V> < / a > < / li >
< li > < a href = "#mp_remove_if_l_p" > mp_remove_if< L, P> < / a > < / li >
< li > < a href = "#mp_partition_l_p" > mp_partition< L, P> < / a > < / li >
< li > < a href = "#mp_sort_l_p" > mp_sort< L, P> < / a > < / li >
< li > < a href = "#mp_find_l_v" > mp_find< L, V> < / a > < / li >
< li > < a href = "#mp_find_if_l_p" > mp_find_if< L, P> < / a > < / li >
< li > < a href = "#mp_reverse_l" > mp_reverse< L> < / a > < / li >
< li > < a href = "#mp_fold_l_v_f" > mp_fold< L, V, F> < / a > < / li >
< li > < a href = "#mp_reverse_fold_l_v_f" > mp_reverse_fold< L, V, F> < / a > < / li >
< li > < a href = "#mp_unique_l" > mp_unique< L> < / a > < / li >
< li > < a href = "#mp_all_of_l_p" > mp_all_of< L, P> < / a > < / li >
< li > < a href = "#mp_none_of_l_p" > mp_none_of< L, P> < / a > < / li >
< li > < a href = "#mp_any_of_l_p" > mp_any_of< L, P> < / a > < / li >
< li > < a href = "#mp_for_each_l_f" > mp_for_each< L> (f)< / a > < / li >
< li > < a href = "#mp_with_index_n_i_f" > mp_with_index< N> (i, f)< / a > < / li >
< / ul >
< / li >
< li > < a href = "#set" > Set Operations, < boost/mp11/set.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_set_contains_s_v" > mp_set_contains< S, V> < / a > < / li >
< li > < a href = "#mp_set_push_back_s_t" > mp_set_push_back< S, T… ​ > < / a > < / li >
< li > < a href = "#mp_set_push_front_s_t" > mp_set_push_front< S, T… ​ > < / a > < / li >
< / ul >
< / li >
< li > < a href = "#map" > Map Operations, < boost/mp11/map.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_map_find_m_k" > mp_map_find< M, K> < / a > < / li >
< li > < a href = "#mp_map_contains_m_k" > mp_map_contains< M, K> < / a > < / li >
< li > < a href = "#mp_map_insert_m_t" > mp_map_insert< M, T> < / a > < / li >
< li > < a href = "#mp_map_replace_m_t" > mp_map_replace< M, T> < / a > < / li >
< li > < a href = "#mp_map_update_m_t_f" > mp_map_update< M, T, F> < / a > < / li >
< li > < a href = "#mp_map_erase_m_k" > mp_map_erase< M, K> < / a > < / li >
< / ul >
< / li >
< li > < a href = "#function" > Helper Metafunctions, < boost/mp11/function.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_void_t" > mp_void< T… ​ > < / a > < / li >
< li > < a href = "#mp_and_t" > mp_and< T… ​ > < / a > < / li >
< li > < a href = "#mp_all_t" > mp_all< T… ​ > < / a > < / li >
< li > < a href = "#mp_or_t" > mp_or< T… ​ > < / a > < / li >
< li > < a href = "#mp_any_t" > mp_any< T… ​ > < / a > < / li >
< li > < a href = "#mp_same_t" > mp_same< T… ​ > < / a > < / li >
< li > < a href = "#mp_plus_t" > mp_plus< T… ​ > < / a > < / li >
< / ul >
< / li >
< li > < a href = "#bind" > Bind, < boost/mp11/bind.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#mp_arg_i" > mp_arg< I> < / a > < / li >
< li > < a href = "#1_9" > _1, … ​ , _9< / a > < / li >
< li > < a href = "#mp_bind_f_t" > mp_bind< F, T… ​ > < / a > < / li >
< li > < a href = "#mp_bind_q_q_t" > mp_bind_q< Q, T… ​ > < / a > < / li >
< li > < a href = "#mp_bind_front_f_t" > mp_bind_front< F, T… ​ > < / a > < / li >
< li > < a href = "#mp_bind_front_q_q_t" > mp_bind_front_q< Q, T… ​ > < / a > < / li >
< li > < a href = "#mp_bind_back_f_t" > mp_bind_back< F, T… ​ > < / a > < / li >
< li > < a href = "#mp_bind_back_q_q_t" > mp_bind_back_q< Q, T… ​ > < / a > < / li >
< / ul >
< / li >
< li > < a href = "#integer_sequence" > Integer Sequences, < boost/mp11/integer_sequence.hpp> < / a >
< ul class = "sectlevel3" >
< li > < a href = "#integer_sequence_t_i" > integer_sequence< T, I… ​ > < / a > < / li >
< li > < a href = "#make_integer_sequence_t_n" > make_integer_sequence< T, N> < / a > < / li >
< li > < a href = "#index_sequence_i" > index_sequence< I… ​ > < / a > < / li >
< li > < a href = "#make_index_sequence_n" > make_index_sequence< N> < / a > < / li >
< li > < a href = "#index_sequence_for_t" > index_sequence_for< T… ​ > < / a > < / li >
< / ul >
< / li >
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< li > < a href = "#tuple" > Tuple Operations, < boost/mp11/tuple.hpp> < / a >
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< ul class = "sectlevel3" >
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< li > < a href = "#tuple_apply_f_tp" > tuple_apply(f, tp)< / a > < / li >
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< li > < a href = "#construct_from_tuple_t_tp" > construct_from_tuple< T> (tp)< / a > < / li >
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< li > < a href = "#tuple_for_each_tp_f" > tuple_for_each(tp, f)< / a > < / li >
< / ul >
< / li >
< / ul >
< / li >
< li > < a href = "#copyright_and_license" > Appendix A: Copyright and License< / a > < / li >
< / ul >
< / div >
< / div >
< div id = "content" >
< div class = "sect1" >
< h2 id = "overview" > Overview< / h2 >
< div class = "sectionbody" >
< div class = "paragraph" >
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< p > Mp11 is a C++11 metaprogramming library for compile-time manipulation of data structures
that contain types. It’ s based on template aliases and variadic templates and implements the
approach outlined in the article
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< a href = "http://pdimov.com/cpp2/simple_cxx11_metaprogramming.html" > "Simple C++ metaprogramming"< / a >
and < a href = "http://pdimov.com/cpp2/simple_cxx11_metaprogramming_2.html" > its sequel< / a > . Reading these
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articles before proceeding with this documentation is < em > highly< / em > recommended.< / p >
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< / div >
< div class = "paragraph" >
< p > The general principles upon which Mp11 is built are that algorithms and metafunctions are
template aliases of the form < code > F< T… ​ > < / code > and data structures are lists of the form < code > L< T… ​ > < / code > ,
with the library placing no requirements on < code > L< / code > . < code > mp_list< T… ​ > < / code > is the built-in list type,
but < code > std::tuple< T… ​ > < / code > , < code > std::pair< T1, T2> < / code > and < code > std::variant< T… ​ > < / code > are also perfectly
legitimate list types, although of course < code > std::pair< T1, T2> < / code > , due to having exactly two elements,
is not resizeable and will consequently not work with algorithms that need to add or remove
elements.< / p >
< / div >
< div class = "paragraph" >
< p > Another distinguishing feature of this approach is that lists (< code > L< T… ​ > < / code > ) have the same form as
metafunctions (< code > F< T… ​ > < / code > ) and can therefore be used as such. For example, applying < code > std::add_pointer_t< / code >
to the list < code > std::tuple< int, float> < / code > by way of < code > mp_transform< std::add_pointer_t, std::tuple< int, float> > < / code >
gives us < code > std::tuple< int*, float*> < / code > , but we can also apply < code > mp_list< / code > to the same tuple:< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > using R = mp_transform< mp_list, std::tuple< int, float> > ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > and get < code > std::tuple< mp_list< int> , mp_list< float> > < / code > .< / p >
< / div >
< / div >
< / div >
< div class = "sect1" >
< h2 id = "definitions" > Definitions< / h2 >
< div class = "sectionbody" >
< div class = "paragraph" >
< p > A < em > list< / em > is a  —   usually but not necessarily variadic  —   template class whose parameters are all types,
for example < code > mp_list< char[], void> < / code > , < code > mp_list< > < / code > , < code > std::tuple< int, float, char> < / code > , < code > std::pair< int, float> < / code > , < code > std::shared_ptr< X> < / code > .< / p >
< / div >
< div class = "paragraph" >
< p > A < em > metafunction< / em > is a class template or a template alias whose parameters are all types, for example < code > std::add_pointer_t< / code > ,
< code > std::is_const< / code > , < code > mp_second< / code > , < code > mp_push_front< / code > , < code > mp_list< / code > , < code > std::tuple< / code > , < code > std::pair< / code > , < code > std::shared_ptr< / code > , or< / p >
< / div >
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< div class = "listingblock" >
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< div class = "content" >
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< pre class = "highlight" > < code > template< class...> using F1 = void;
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template< class T> using F2 = T*;
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template< class... T> using F3 = std::integral_constant< std::size_t, sizeof...(T)> ;< / code > < / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > A < em > quoted metafunction< / em > is a class with a public metafunction member called < code > fn< / code > , for example< / p >
< / div >
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< div class = "listingblock" >
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< div class = "content" >
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< pre class = "highlight" > < code > struct Q1 { template< class...> using fn = void; };
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struct Q2 { template< class T> using fn = T*; };
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struct Q3 { template< class... T> using fn =
std::integral_constant< std::size_t, sizeof...(T)> ; };< / code > < / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > An < em > integral constant type< / em > is a class with a public member < code > value< / code > that is an integral constant in the C++ sense. For example,
< code > std::integral_constant< int, 7> < / code > , or< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > struct N { static int constexpr value = 2; };< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > A < em > set< / em > is a list whose elements are unique.< / p >
< / div >
< div class = "paragraph" >
< p > A < em > map< / em > is a list of lists, the inner lists having at least one element (the key.) The keys of the map must be unique. For example,< / p >
< / div >
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< div class = "listingblock" >
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< div class = "content" >
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< pre class = "highlight" > < code > using M1 = std::tuple< std::pair< int, int*> , std::pair< float, float*> ,
std::pair< void, void*> > ;
using M2 = mp_list< mp_list< int, int*> , mp_list< float> ,
mp_list< char, char[1], char[2]> > ;< / code > < / pre >
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< / div >
< / div >
< / div >
< / div >
< div class = "sect1" >
< h2 id = "examples" > Examples< / h2 >
< div class = "sectionbody" >
< div class = "sect2" >
< h3 id = "generating_test_cases" > Generating Test Cases< / h3 >
< div class = "paragraph" >
< p > Let’ s suppose that we have written a metafunction < code > result< T, U> < / code > :< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using promote = typename std::common_type< T, int> ::type;
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template< class T, class U> using result =
typename std::common_type< promote< T> , promote< U> > ::type;< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > that ought to represent the result of an arithmetic operation on the integer types < code > T< / code > and < code > U< / code > ,
for example < code > t + u< / code > . We want to test whether < code > result< T, U> < / code > gives correct results for various combinations
of < code > T< / code > and < code > U< / code > , so we write the function< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class T1, class T2> void test_result()
{
using T3 = decltype( T1() + T2() );
using T4 = result< T1, T2> ;
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std::cout < < ( std::is_same< T3, T4> ::value? "[PASS]": "[FAIL]" ) < < std::endl;
}< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > and then need to call it a substantial number of times:< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > int main()
{
test_result< char, char> ();
test_result< char, short> ();
test_result< char, int> ();
test_result< char, unsigned> ();
// ...
}< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Writing all those type combinations by hand is unwieldy, error prone, and worst of all, boring. This is
how we can leverage Mp11 to automate the task:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > #include < boost/mp11.hpp>
#include < boost/core/demangle.hpp>
#include < type_traits>
#include < iostream>
#include < typeinfo>
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using namespace boost::mp11;
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template< class T> std::string name()
{
return boost::core::demangle( typeid(T).name() );
}
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template< class T> using promote = typename std::common_type< T, int> ::type;
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template< class T, class U> using result =
typename std::common_type< promote< T> , promote< U> > ::type;
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template< class T1, class T2> void test_result( mp_list< T1, T2> const& )
{
using T3 = decltype( T1() + T2() );
using T4 = result< T1, T2> ;
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std::cout < < ( std::is_same< T3, T4> ::value? "[PASS] ": "[FAIL] " )
< < name< T1> () < < " + " < < name< T2> () < < " -> " < < name< T3> ()
< < ", result: " < < name< T4> () < < std::endl;
}
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int main()
{
using L = std::tuple< char, short, int, unsigned, long, unsigned long> ;
tuple_for_each( mp_product< mp_list, L, L> (), [](auto& & x){ test_result(x); } );
}< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > How does it work?< / p >
< / div >
< div class = "paragraph" >
< p > < code > mp_product< F, L1, L2> < / code > calls < code > F< T1, T2> < / code > where < code > T1< / code > varies over the elements of < code > L1< / code > and < code > T2< / code > varies over
the elements of < code > L2< / code > , as if by executing two nested loops. It then returns a list of these results, of the same
type as < code > L1< / code > .< / p >
< / div >
< div class = "paragraph" >
< p > In our case, both lists are the same < code > std::tuple< / code > , and < code > F< / code > is < code > mp_list< / code > , so < code > mp_product< mp_list, L, L> < / code > will get us
< code > std::tuple< mp_list< char, char> , mp_list< char, short> , mp_list< char, int> , … ​ , mp_list< unsigned long, long> , mp_list< unsigned long, unsigned long> > < / code > .< / p >
< / div >
< div class = "paragraph" >
< p > We then default-construct this tuple and pass it to < code > tuple_for_each< / code > . < code > tuple_for_each(tp, f)< / code > calls < code > f< / code > for every
tuple element; we use a (C++14) lambda that calls < code > test_result< / code > .< / p >
< / div >
< div class = "paragraph" >
< p > In pure C++11, we can’ t use a lambda with an < code > auto& & < / code > parameter, so we’ ll have to make < code > test_result< / code > a function object with
a templated < code > operator()< / code > and pass that to < code > tuple_for_each< / code > directly:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > struct test_result
{
template< class T1, class T2> void operator()( mp_list< T1, T2> const& ) const
{
using T3 = decltype( T1() + T2() );
using T4 = result< T1, T2> ;
std::cout < < ( std::is_same< T3, T4> ::value? "[PASS] ": "[FAIL] " )
< < name< T1> () < < " + " < < name< T2> () < < " -> " < < name< T3> ()
< < ", result: " < < name< T4> () < < std::endl;
}
};
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int main()
{
using L = std::tuple< char, short, int, unsigned, long, unsigned long> ;
tuple_for_each( mp_product< mp_list, L, L> (), test_result() );
}< / code > < / pre >
< / div >
< / div >
< / div >
< div class = "sect2" >
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< h3 id = "writing_common_type_specializations" > Writing common_type Specializations< / h3 >
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< div class = "paragraph" >
< p > The standard trait < code > std::common_type< / code > , used to obtain a type to which all of its arguments can convert without
unnecessary loss of precision, can be user-specialized when its default implementation (based on the ternary < code > ?:< / code >
operator) is unsuitable.< / p >
< / div >
< div class = "paragraph" >
< p > Let’ s write a < code > common_type< / code > specialization for two < code > std::tuple< / code > arguments. For that, we need a metafunction that
applies < code > std::common_type< / code > to each pair of elements and gathers the results into a tuple:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class... T> using common_type_t =
typename std::common_type< T...> ::type; // standard in C++14
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template< class Tp1, class Tp2> using common_tuple =
mp_transform< common_type_t, Tp1, Tp2> ;< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > then specialize < code > common_type< / code > to use it:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > namespace std
{
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template< class... T1, class... T2>
struct common_type< std::tuple< T1...> , std::tuple< T2...> > :
mp_defer< common_tuple, std::tuple< T1...> , std::tuple< T2...> >
{
};
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} // std< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > (There is no need to specialize < code > std::common_type< / code > for more than two arguments - it takes care of synthesizing the appropriate semantics from
the binary case.)< / p >
< / div >
< div class = "paragraph" >
< p > The subtlety here is the use of < code > mp_defer< / code > . We could have defined a nested < code > type< / code > to < code > common_tuple< std::tuple< T1… ​ > , std::tuple< T2… ​ > > < / code > ,
and it would still have worked in all valid cases. By letting < code > mp_defer< / code > define < code > type< / code > , though, we make our specialization < em > SFINAE-friendly< / em > .< / p >
< / div >
< div class = "paragraph" >
< p > That is, when our < code > common_tuple< / code > causes a substitution failure instead of a hard error, < code > mp_defer< / code > will not define a nested < code > type< / code > ,
and < code > common_type_t< / code > , which is defined as < code > typename common_type< … ​ > ::type< / code > , will also cause a substitution failure.< / p >
< / div >
< div class = "paragraph" >
< p > As another example, consider the hypothetical type < code > expected< T, E… ​ > < / code > that represents either a successful return with a value of < code > T< / code > ,
or an unsucessful return with an error code of some type in the list < code > E… ​ < / code > . The common type of < code > expected< T1, E1, E2, E3> < / code > and
< code > expected< T2, E1, E4, E5> < / code > is < code > expected< common_type_t< T1, T2> , E1, E2, E3, E4, E5> < / code > . That is, the possible return values are
combined into their common type, and we take the union of the set of error types.< / p >
< / div >
< div class = "paragraph" >
< p > Therefore,< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class T1, class E1, class T2, class E2> using common_expected =
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mp_rename< mp_push_front< mp_unique< mp_append< E1, E2> > , common_type_t< T1, T2> > ,
expected> ;
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namespace std
{
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template< class T1, class... E1, class T2, class... E2>
struct common_type< expected< T1, E1...> , expected< T2, E2...> > :
mp_defer< common_expected, T1, mp_list< E1...> , T2, mp_list< E2...> >
{
};
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} // std< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Here we’ ve taken a different tack; instead of passing the < code > expected< / code > types to < code > common_expected< / code > , we’ re passing the < code > T< / code > types and lists of
the < code > E< / code > types. This makes our job easier. < code > mp_unique< mp_append< E1, E2> > < / code > gives us the concatenation of < code > E1< / code > and < code > E2< / code > with the duplicates
removed; we then add < code > common_type_t< T1, T2> < / code > to the front via < code > mp_push_front< / code > ; and finally, we < code > mp_rename< / code > the resultant < code > mp_list< / code >
to < code > expected< / code > .< / p >
< / div >
< / div >
< div class = "sect2" >
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< h3 id = "fixing_tuple_cat" > Fixing tuple_cat< / h3 >
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< div class = "paragraph" >
< p > The article < a href = "http://pdimov.com/cpp2/simple_cxx11_metaprogramming.html#" > Simple C++11 metaprogramming< / a > builds an
implementation of the standard function < code > tuple_cat< / code > , with the end result given below:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class L> using F = mp_iota< mp_size< L> > ;
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template< class R, class...Is, class... Ks, class Tp>
R tuple_cat_( mp_list< Is...> , mp_list< Ks...> , Tp tp )
{
return R{ std::get< Ks::value> (std::get< Is::value> (tp))... };
}
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template< class... Tp,
class R = mp_append< std::tuple< > , typename std::remove_reference< Tp> ::type...> >
R tuple_cat( Tp & & ... tp )
{
std::size_t const N = sizeof...(Tp);
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// inner
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using list1 = mp_list<
mp_rename< typename std::remove_reference< Tp> ::type, mp_list> ...> ;
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using list2 = mp_iota_c< N> ;
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using list3 = mp_transform< mp_fill, list1, list2> ;
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using inner = mp_apply< mp_append, list3> ;
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// outer
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using list4 = mp_transform< F, list1> ;
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using outer = mp_apply< mp_append, list4> ;
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//
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return tuple_cat_< R> ( inner(), outer(),
std::forward_as_tuple( std::forward< Tp> (tp)... ) );
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}< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > This function, however, is not entirely correct, in that it doesn’ t handle some cases properly. For example,
trying to concatenate tuples containing move-only elements such as < code > unique_ptr< / code > fails:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > std::tuple< std::unique_ptr< int> > t1;
std::tuple< std::unique_ptr< float> > t2;
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auto result = ::tuple_cat( std::move( t1 ), std::move( t2 ) );< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Trying to concatenate < code > const< / code > tuples fails:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > std::tuple< int> const t1;
std::tuple< float> const t2;
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auto result = ::tuple_cat( t1, t2 );< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > And finally, the standard < code > tuple_cat< / code > is specified to work on arbitrary tuple-like types (that is, all types
that support < code > tuple_size< / code > , < code > tuple_element< / code > , and < code > get< / code > ), while our implementation only works with < code > tuple< / code > and
< code > pair< / code > . < code > std::array< / code > , for example, fails:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > std::array< int, 2> t1{ 1, 2 };
std::array< float, 3> t2{ 3.0f, 4.0f, 5.0f };
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auto result = ::tuple_cat( t1, t2 );< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Let’ s fix these one by one. Support for move-only types is easy, if one knows where to look. The problem is
that < code > Tp< / code > that we’ re passing to the helper < code > tuple_cat_< / code > is (correctly) < code > tuple< unique_ptr< int> & & , unique_ptr< float> & & > < / code > ,
but < code > std::get< 0> (tp)< / code > still returns < code > unique_ptr< int> & < / code > , because < code > tp< / code > is an lvalue. This behavior is a bit
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surprising, but is intended to prevent inadvertent double moves.< / p >
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< / div >
< div class = "paragraph" >
< p > Long story short, we need < code > std::move(tp)< / code > in < code > tuple_cat_< / code > to make < code > tp< / code > an rvalue:< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class R, class...Is, class... Ks, class Tp>
R tuple_cat_( mp_list< Is...> , mp_list< Ks...> , Tp tp )
{
return R{ std::get< Ks::value> (std::get< Is::value> (std::move(tp)))... };
}< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Next, < code > const< / code > -qualified tuples. The issue here is that we’ re stripping references from the input tuples, but not
< code > const< / code > . As a result, we’ re trying to manipulate types such as < code > tuple< int> const< / code > with Mp11 algorithms, and these
types do not fit the list concept. We just need to strip qualifiers as well, by defining the useful < code > remove_cv_ref< / code >
primitive that is inexplicably missing from the standard library:< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T> using remove_cv_ref = typename std::remove_cv<
typename std::remove_reference< T> ::type> ::type;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > and then by using < code > remove_cv_ref< Tp> < / code > in place of < code > typename std::remove_reference< Tp> ::type< / code > :< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class... Tp,
class R = mp_append< std::tuple< > , remove_cv_ref< Tp> ...> >
R tuple_cat( Tp & & ... tp )
{
std::size_t const N = sizeof...(Tp);
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// inner
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using list1 = mp_list< mp_rename< remove_cv_ref< Tp> , mp_list> ...> ;
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// ...< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Finally, tuple-like types. We’ ve so far exploited the fact that < code > std::pair< / code > and < code > std::tuple< / code > are valid Mp11 lists,
but in general, arbitrary tuple-like types aren’ t, so we need to convert them into such. For that, we’ ll need to
define a metafunction < code > from_tuple_like< / code > that will take an arbitrary tuple-like type and will return, in our case,
the corresponding < code > mp_list< / code > .< / p >
< / div >
< div class = "paragraph" >
< p > Technically, a more principled approach would’ ve been to return < code > std::tuple< / code > , but here < code > mp_list< / code > will prove more
convenient.< / p >
< / div >
< div class = "paragraph" >
< p > What we need is, given a tuple-like type < code > Tp< / code > , to obtain < code > mp_list< std::tuple_element< 0, Tp> ::type, std::tuple_element< 1, Tp> ::type,
… ​ , std::tuple_element< N-1, Tp> ::type> < / code > , where < code > N< / code > is < code > tuple_size< Tp> ::value< / code > . Here’ s one way to do it:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class T, class I> using tuple_element =
typename std::tuple_element< I::value, T> ::type;
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template< class T> using from_tuple_like =
mp_product< tuple_element, mp_list< T> , mp_iota< std::tuple_size< T> > > ;< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > (< code > mp_iota< N> < / code > is an algorithm that returns an < code > mp_list< / code > with elements < code > mp_size_t< 0> < / code > , < code > mp_size_t< 1> < / code > , … ​ , < code > mp_size_t< N-1> < / code > .)< / p >
< / div >
< div class = "paragraph" >
< p > Remember that < code > mp_product< F, L1, L2> < / code > performs the equivalent of two nested loops over the elements of < code > L1< / code > and < code > L2< / code > ,
applying < code > F< / code > to the two variables and gathering the result. In our case < code > L1< / code > consists of the single element < code > T< / code > , so
only the second loop (over < code > mp_iota< N> < / code > , where < code > N< / code > is < code > tuple_size< T> < / code > ), remains, and we get a list of the same type
as < code > L1< / code > (an < code > mp_list< / code > ) with contents < code > tuple_element< T, mp_size_t< 0> > < / code > , < code > tuple_element< T, mp_size_t< 1> > < / code > , … ​ ,
< code > tuple_element< T, mp_size_t< N-1> > < / code > .< / p >
< / div >
< div class = "paragraph" >
< p > For completeness’ s sake, here’ s another, more traditional way to achieve the same result:< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T> using from_tuple_like =
mp_transform_q< mp_bind_front< tuple_element, T> , mp_iota< std::tuple_size< T> > > ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > With all these fixes applied, our fully operational < code > tuple_cat< / code > now looks like this:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class L> using F = mp_iota< mp_size< L> > ;
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template< class R, class...Is, class... Ks, class Tp>
R tuple_cat_( mp_list< Is...> , mp_list< Ks...> , Tp tp )
{
return R{ std::get< Ks::value> (std::get< Is::value> (std::move(tp)))... };
}
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template< class T> using remove_cv_ref = typename std::remove_cv<
typename std::remove_reference< T> ::type> ::type;
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template< class T, class I> using tuple_element =
typename std::tuple_element< I::value, T> ::type;
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template< class T> using from_tuple_like =
mp_product< tuple_element, mp_list< T> , mp_iota< std::tuple_size< T> > > ;
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template< class... Tp,
class R = mp_append< std::tuple< > , from_tuple_like< remove_cv_ref< Tp> > ...> >
R tuple_cat( Tp & & ... tp )
{
std::size_t const N = sizeof...(Tp);
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// inner
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using list1 = mp_list< from_tuple_like< remove_cv_ref< Tp> > ...> ;
using list2 = mp_iota_c< N> ;
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using list3 = mp_transform< mp_fill, list1, list2> ;
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using inner = mp_apply< mp_append, list3> ;
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// outer
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using list4 = mp_transform< F, list1> ;
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using outer = mp_apply< mp_append, list4> ;
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//
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return tuple_cat_< R> ( inner(), outer(),
std::forward_as_tuple( std::forward< Tp> (tp)... ) );
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}< / code > < / pre >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "computing_return_types" > Computing Return Types< / h3 >
< div class = "paragraph" >
< p > C++17 has a standard variant type, called < code > std::variant< / code > . It also defines a function template
< code > std::visit< / code > that can be used to apply a function to the contained value of one or more variants.
So for instance, if the variant < code > v1< / code > contains < code > 1< / code > , and the variant < code > v2< / code > contains < code > 2.0f< / code > ,
< code > std::visit(f, v1, v2)< / code > will call < code > f(1, 2.0f)< / code > .< / p >
< / div >
< div class = "paragraph" >
< p > However, < code > std::visit< / code > has one limitation: it cannot return a result unless all
possible applications of the function have the same return type. If, for instance, < code > v1< / code > and < code > v2< / code >
are both of type < code > std::variant< short, int, float> < / code > ,< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > std::visit( []( auto const& x, auto const& y ){ return x + y; }, v1, v2 );< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > will fail to compile because the result of < code > x + y< / code > can be either < code > int< / code > or < code > float< / code > depending on
what < code > v1< / code > and < code > v2< / code > hold.< / p >
< / div >
< div class = "paragraph" >
< p > A type that can hold either < code > int< / code > or < code > float< / code > already exists, called, surprisingly enough, < code > std::variant< int, float> < / code > .
Let’ s write our own function template < code > rvisit< / code > that is the same as < code > visit< / code > but returns a < code > variant< / code > :< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > template< class F, class... V> auto rvisit( F& & f, V& & ... v )
{
using R = /*...*/;
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return std::visit( [& ]( auto& & ... x )
{ return R( std::forward< F> (f)( std::forward< decltype(x)> (x)... ) ); },
std::forward< V> ( v )... );
}< / code > < / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > What this does is basically calls < code > std::visit< / code > to do the work, but instead of passing it < code > f< / code > , we pass a lambda that does the same as < code > f< / code > except
it converts the result to a common type < code > R< / code > . < code > R< / code > is supposed to be < code > std::variant< … ​ > < / code > where the ellipsis denotes the return types of
calling < code > f< / code > with all possible combinations of variant values.< / p >
< / div >
< div class = "paragraph" >
< p > We’ ll first define a helper quoted metafunction < code > Qret< F> < / code > that returns the result of the application of < code > F< / code > to arguments of type < code > T… ​ < / code > :< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class F> struct Qret
{
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template< class... T> using fn =
decltype( std::declval< F> ()( std::declval< T> ()... ) );
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};< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > (Unfortunately, we can’ t just define this metafunction inside < code > rvisit< / code > ; the language prohibits defining template aliases inside functions.)< / p >
< / div >
< div class = "paragraph" >
< p > With < code > Qret< / code > in hand, a < code > variant< / code > of the possible return types is just a matter of applying it over the possible combinations of the variant values:< / p >
< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > using R = mp_product_q< Qret< F> , std::remove_reference_t< V> ...> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Why does this work? < code > mp_product< F, L1< T1… ​ > , L2< T2… ​ > , … ​ , Ln< Tn… ​ > > < / code > returns < code > L1< F< U1, U2, … ​ , Un> , … ​ > < / code > , where < code > Ui< / code > traverse all
possible combinations of list values. Since in our case all < code > Li< / code > are < code > std::variant< / code > , the result will also be < code > std::variant< / code > . (< code > mp_product_q< / code > is
the same as < code > mp_product< / code > , but for quoted metafunctions such as our < code > Qret< F> < / code > .)< / p >
< / div >
< div class = "paragraph" >
< p > One more step remains. Suppose that, as above, we’ re passing two variants of type < code > std::variant< short, int, float> < / code > and < code > F< / code > is
< code > []( auto const& x, auto const& y ){ return x + y; }< / code > . This will generate < code > R< / code > of length 9, one per each combination, but many of those
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elements will be the same, either < code > int< / code > or < code > float< / code > , and we need to filter out the duplicates. So, we pass the result to < code > mp_unique< / code > :< / p >
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< / div >
< div class = "literalblock" >
< div class = "content" >
< pre > using R = mp_unique< mp_product_q< Qret< F> , std::remove_reference_t< V> ...> > ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > and we’ re done:< / p >
< / div >
< div class = "listingblock" >
< div class = "content" >
< pre class = "highlight" > < code > #include < boost/mp11.hpp>
#include < boost/core/demangle.hpp>
#include < variant>
#include < type_traits>
#include < typeinfo>
#include < iostream>
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using namespace boost::mp11;
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template< class F> struct Qret
{
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template< class... T> using fn =
decltype( std::declval< F> ()( std::declval< T> ()... ) );
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};
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template< class F, class... V> auto rvisit( F& & f, V& & ... v )
{
using R = mp_unique< mp_product_q< Qret< F> , std::remove_reference_t< V> ...> > ;
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return std::visit( [& ]( auto& & ... x )
{ return R( std::forward< F> (f)( std::forward< decltype(x)> (x)... ) ); },
std::forward< V> ( v )... );
}
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template< class T> std::string name()
{
return boost::core::demangle( typeid(T).name() );
}
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template< class V> void print_variant( char const * n, V const& v )
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{
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std::cout < < "(" < < name< decltype(v)> () < < ")" < < n < < ": ";
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std::visit( []( auto const& x )
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{ std::cout < < "(" < < name< decltype(x)> () < < ")" < < x < < std::endl; }, v );
}
int main()
{
std::variant< char, int, float> v1( 1 );
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print_variant( "v1", v1 );
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std::variant< short, int, double> v2( 3.14 );
print_variant( "v2", v2 );
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auto v3 = rvisit( []( auto const& x, auto const& y ){ return x + y; }, v1, v2 );
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print_variant( "v3", v3 );
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}< / code > < / pre >
< / div >
< / div >
< / div >
< / div >
< / div >
< div class = "sect1" >
< h2 id = "reference" > Reference< / h2 >
< div class = "sectionbody" >
< div class = "paragraph" >
< p > The contents of the library are in namespace < code > boost::mp11< / code > .< / p >
< / div >
< div class = "sect2" >
< h3 id = "integral" > Integral Constants, < boost/mp11/integral.hpp> < / h3 >
< div class = "paragraph" >
< p > For an Mp11 integral constant type < code > T< / code > , < code > T::value< / code > is an integral constant in the C++ sense.< / p >
< / div >
< div class = "sect3" >
< h4 id = "mp_bool_b" > mp_bool< B> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< bool B> using mp_bool = std::integral_constant< bool, B> ;< / pre >
< / div >
< / div >
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< div class = "paragraph" >
< p > Same as < code > std::bool_constant< / code > in C++17.< / p >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_true" > mp_true< / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > using mp_true = mp_bool< true> ;< / pre >
< / div >
< / div >
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< div class = "paragraph" >
< p > Same as < code > std::true_type< / code > .< / p >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_false" > mp_false< / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > using mp_false = mp_bool< false> ;< / pre >
< / div >
< / div >
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< div class = "paragraph" >
< p > Same as < code > std::false_type< / code > .< / p >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_to_bool_t" > mp_to_bool< T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T> using mp_to_bool = mp_bool< static_cast< bool> (T::value)> ;< / pre >
< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_not_t" > mp_not< T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T> using mp_not = mp_bool< !T::value > ;< / pre >
< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_int_i" > mp_int< I> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< int I> using mp_int = std::integral_constant< int, I> ;< / pre >
< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_size_t_n" > mp_size_t< N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< std::size_t N> using mp_size_t = std::integral_constant< std::size_t, N> ;< / pre >
< / div >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "list" > List Operations, < boost/mp11/list.hpp> < / h3 >
< div class = "sect3" >
< h4 id = "mp_list_t" > mp_list< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> struct mp_list {};< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_list< / code > is the standard list type of Mp11, although the library is not restricted to it and can operate on arbitrary class templates
such as < code > std::tuple< / code > or < code > std::variant< / code > . Even < code > std::pair< / code > can be used if the transformation does not alter the number of the elements in
the list.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_size_l" > mp_size< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_size = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_size< L> < / code > returns the number of elements in the list < code > L< / code > , as a < code > mp_size_t< / code > . In other words, < code > mp_size< L< T… ​ > > < / code > is an alias for
< code > mp_size_t< sizeof… ​ (T)> < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 1. Using mp_size with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = mp_list< > ;
using R1 = mp_size< L1> ; // mp_size_t< 0> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 2. Using mp_size with std::pair< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = std::pair< int, int> ;
using R2 = mp_size< L2> ; // mp_size_t< 2> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 3. Using mp_size with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L3 = std::tuple< float> ;
using R3 = mp_size< L3> ; // mp_size_t< 1> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_empty_l" > mp_empty< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_empty = mp_bool< mp_size< L> ::value == 0> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_empty< L> < / code > is an alias for < code > mp_true< / code > if the list < code > L< / code > is empty, for < code > mp_false< / code > otherwise.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 4. Using mp_empty with std::tuple< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< float> ;
using R1 = mp_empty< L1> ; // mp_false
using L2 = std::tuple< > ;
using R2 = mp_empty< L2> ; // mp_true< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_front_l" > mp_front< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_front = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_front< L> < / code > is the first element of the list < code > L< / code > . That is, < code > mp_front< L< T1, T… ​ > > < / code > is an alias for < code > T1< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 5. Using mp_front with std::pair< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::pair< int, float> ;
using R1 = mp_front< L1> ; // int< / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 6. Using mp_front with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = std::tuple< float, double, long double> ;
using R2 = mp_front< L2> ; // float< / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 7. Using mp_front with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L3 = mp_list< char[1], char[2], char[3], char[4]> ;
using R3 = mp_front< L3> ; // char[1]< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_pop_front_l" > mp_pop_front< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_pop_front = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_pop_front< L> < / code > removes the first element of the list < code > L< / code > . That is, < code > mp_pop_front< L< T1, T… ​ > > < / code > is an alias for < code > L< T… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 8. Using mp_pop_front with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::tuple< float, double, long double> ;
using R1 = mp_pop_front< L1> ; // std::tuple< double, long double> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 9. Using mp_pop_front with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = mp_list< void> ;
using R2 = mp_pop_front< L2> ; // mp_list< > < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_first_l" > mp_first< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_first = mp_front< L> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_first< / code > is another name for < code > mp_front< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_rest_l" > mp_rest< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_rest = mp_pop_front< L> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_rest< / code > is another name for < code > mp_pop_front< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_second_l" > mp_second< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_second = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_second< L> < / code > is the second element of the list < code > L< / code > . That is, < code > mp_second< L< T1, T2, T… ​ > > < / code > is an alias for < code > T2< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 10. Using mp_second with std::pair< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::pair< int, float> ;
using R1 = mp_second< L1> ; // float< / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 11. Using mp_second with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = std::tuple< float, double, long double> ;
using R2 = mp_second< L2> ; // double< / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 12. Using mp_second with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L3 = mp_list< char[1], char[2], char[3], char[4]> ;
using R3 = mp_second< L3> ; // char[2]< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_third_l" > mp_third< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_third = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_third< L> < / code > is the third element of the list < code > L< / code > . That is, < code > mp_third< L< T1, T2, T3, T… ​ > > < / code > is an alias for < code > T3< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 13. Using mp_third with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::tuple< float, double, long double> ;
using R1 = mp_third< L1> ; // long double< / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 14. Using mp_third with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = mp_list< char[1], char[2], char[3], char[4]> ;
using R2 = mp_third< L2> ; // char[3]< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_push_front_l_t" > mp_push_front< L, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class... T> using mp_push_front = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_push_front< L, T… ​ > < / code > inserts the elements < code > T… ​ < / code > at the front of the list < code > L< / code > . That is, < code > mp_push_front< L< U… ​ > , T… ​ > < / code >
is an alias for < code > L< T… ​ , U… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 15. Using mp_push_front with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::tuple< double, long double> ;
using R1 = mp_push_front< L1, float> ; // std::tuple< float, double, long double> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 16. Using mp_push_front with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = mp_list< void> ;
using R2 = mp_push_front< L2, char[1], char[2]> ; // mp_list< char[1], char[2], void> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_push_back_l_t" > mp_push_back< L, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class... T> using mp_push_back = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_push_back< L, T… ​ > < / code > inserts the elements < code > T… ​ < / code > at the back of the list < code > L< / code > . That is, < code > mp_push_back< L< U… ​ > , T… ​ > < / code >
is an alias for < code > L< U… ​ , T… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 17. Using mp_push_back with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::tuple< double, long double> ;
using R1 = mp_push_back< L1, float> ; // std::tuple< double, long double, float> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 18. Using mp_push_back with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = mp_list< void> ;
using R2 = mp_push_back< L2, char[1], char[2]> ; // mp_list< void, char[1], char[2]> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_rename_l_y" > mp_rename< L, Y> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class Y> using mp_rename = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_rename< L, Y> < / code > changes the type of the list < code > L< / code > to < code > Y< / code > . That is, < code > mp_rename< L< T… ​ > , Y> < / code > is an alias for < code > Y< T… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 19. Using mp_rename to rename std::pair to std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::pair< double, long double> ;
using R1 = mp_rename< L1, std::tuple> ; // std::tuple< double, long double> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 20. Using mp_rename to rename std::tuple to mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = std::tuple< void> ;
using R2 = mp_rename< L2, mp_list> ; // mp_list< void> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_apply_f_l" > mp_apply< F, L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class L> using mp_apply = mp_rename< L, F> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_apply< F, L> < / code > applies the metafunction < code > F< / code > to the contents of the list < code > L< / code > , that is, < code > mp_apply< F, L< T… ​ > > < / code > is an alias for < code > F< T… ​ > < / code > .
(< code > mp_apply< / code > is the same as < code > mp_rename< / code > with the arguments reversed.)< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 21. Using mp_apply with std::pair< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::pair< double, long double> ;
using R1 = mp_apply< std::is_same, L1> ; // std::is_same< double, long double> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_apply_q_q_l" > mp_apply_q< Q, L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class Q, class L> using mp_apply_q = mp_apply< Q::template fn, L> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_apply< / code > , but takes a quoted metafunction.< / p >
< / div >
< div class = "listingblock" >
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< div class = "title" > Code Example 22. Using mp_apply_q with mp_bind_front< / div >
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< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< double, long double> ;
using L2 = mp_list< int, long> ;
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using R1 = mp_apply_q< mp_bind_front< mp_push_back, L1> , L2> ;
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// R1 is std::tuple< double, long double, int, long> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_append_l" > mp_append< L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... L> using mp_append = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_append< L… ​ > < / code > concatenates the lists in < code > L… ​ < / code > into a single list that has the same type as the first list. < code > mp_append< > < / code >
is an alias for < code > mp_list< > < / code > . < code > mp_append< L1< T1… ​ > , L2< T2… ​ > , … ​ , Ln< Tn… ​ > > < / code > is an alias for < code > L1< T1… ​ , T2… ​ , … ​ , Tn… ​ > < / code > .< / p >
< / div >
< div class = "listingblock" >
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< div class = "title" > Code Example 23. Using mp_append with lists of various types< / div >
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< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< double, long double> ;
using L2 = mp_list< int> ;
using L3 = std::pair< short, long> ;
using L4 = mp_list< > ;
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using R1 = mp_append< L1, L2, L3, L4> ;
// std::tuple< double, long double, int, short, long> < / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_replace_front_l_t" > mp_replace_front< L, T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class T> using mp_replace_front = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_replace_front< L, T> < / code > replaces the first element of the list < code > L< / code > with < code > T< / code > . That is, < code > mp_replace_front< L< U1, U… ​ > , T> < / code > is
an alias for < code > L< T, U… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 24. Using mp_replace_front with std::pair< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::pair< int, float> ;
using R1 = mp_replace_front< L1, void> ; // std::pair< void, float> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 25. Using mp_replace_front with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = std::tuple< float, double, long double> ;
using R2 = mp_replace_front< L2, void> ; // std::tuple< void, double, long double> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 26. Using mp_replace_front with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L3 = mp_list< char[1], char[2], char[3], char[4]> ;
using R3 = mp_replace_front< L3, void> ; // mp_list< void, char[2], char[3], char[4]> ;< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_replace_first_l_t" > mp_replace_first< L, T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class T> using mp_replace_first = mp_replace_front< L, T> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_replace_first< / code > is another name for < code > mp_replace_front< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_replace_second_l_t" > mp_replace_second< L, T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class T> using mp_replace_second = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_replace_second< L, T> < / code > replaces the second element of the list < code > L< / code > with < code > T< / code > . That is, < code > mp_replace_second< L< U1, U2, U… ​ > , T> < / code >
is an alias for < code > L< U1, T, U… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 27. Using mp_replace_second with std::pair< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::pair< int, float> ;
using R1 = mp_replace_second< L1, void> ; // std::pair< int, void> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 28. Using mp_replace_second with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = std::tuple< float, double, long double> ;
using R2 = mp_replace_second< L2, void> ; // std::tuple< float, void, long double> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 29. Using mp_replace_front with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L3 = mp_list< char[1], char[2], char[3], char[4]> ;
using R3 = mp_replace_second< L3, void> ; // mp_list< char[1], void, char[3], char[4]> ;< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_replace_third_l_t" > mp_replace_third< L, T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class T> using mp_replace_third = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_replace_third< L, T> < / code > replaces the third element of the list < code > L< / code > with < code > T< / code > . That is, < code > mp_replace_third< L< U1, U2, U3, U… ​ > , T> < / code >
is an alias for < code > L< U1, U2, T, U… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 30. Using mp_replace_third with std::tuple< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L1 = std::tuple< float, double, long double> ;
using R1 = mp_replace_third< L1, void> ; // std::tuple< float, double, void> < / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 31. Using mp_replace_third with mp_list< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using L2 = mp_list< char[1], char[2], char[3], char[4]> ;
using R2 = mp_replace_third< L2, void> ; // mp_list< char[1], char[2], void, char[4]> ;< / code > < / pre >
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< / div >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "utility" > Utility Components, < boost/mp11/utility.hpp> < / h3 >
< div class = "sect3" >
< h4 id = "mp_identity_t" > mp_identity< T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T> struct mp_identity
{
using type = T;
};< / pre >
< / div >
< / div >
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< div class = "paragraph" >
< p > < code > mp_identity< / code > is a simple < em > transformation type trait< / em > (as per the C++ standard)
that just returns the same type. It’ s useful both as such, and as a type wrapper
useful for passing types as values to functions.< / p >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 32. Using mp_identity as a type trait< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using addp_if_not_ref =
typename mp_if< std::is_reference< T> , mp_identity< T> , std::add_pointer< T> > ::type;< / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 33. Using mp_identity to protect qualifiers and references< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> void print1()
{
std::cout < < typeid(T).name() < < std::endl;
}
template< class T> void print2()
{
std::cout < < typeid(mp_identity< T> ).name() < < std::endl;
}
int main()
{
print1< int const& > (); // 'int'
print2< int const& > (); // 'mp_identity< int const & > '
}< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_identity_t_t" > mp_identity_t< T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class T> using mp_identity_t = typename mp_identity< T> ::type;< / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_inherit_t" > mp_inherit< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> struct mp_inherit: T... {};< / pre >
< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_if_c_c_t_e" > mp_if_c< C, T, E… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< bool C, class T, class... E> using mp_if_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_if_c< true, T, E… ​ > < / code > is an alias for < code > T< / code > . < code > mp_if_c< false, T, E> < / code > is an alias for < code > E< / code > . Otherwise, the result is a substitution failure.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 34. Using mp_if_c to select between two alternatives< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using R1 = mp_if_c< true, int, void> ; // int
using R2 = mp_if_c< false, int, void> ; // void< / code > < / pre >
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< / div >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 35. Using mp_if_c to fail substitution when a condition is not met< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > template< class I> using void_if_5 = mp_if_c< I::value == 5, void> ;< / code > < / pre >
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< / div >
< / div >
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< div class = "paragraph" >
< p > This example returns < code > void< / code > when < code > I::value< / code > is 5, and generates a substitution failure
otherwise. It’ s the same as < code > std::enable_if_t< I::value == 5> < / code > in C++14, or
< code > typename std::enable_if< I::value == 5> ::type< / code > in C++11.< / p >
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< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_if_c_t_e" > mp_if< C, T, E… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class C, class T, class E...> using mp_if =
mp_if_c< static_cast< bool> (C::value), T, E...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Like < code > mp_if_c< / code > , but the first argument is a type.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 36. Using mp_if to select between two alternatives< / div >
< div class = "content" >
< pre class = "highlight" > < code > using R1 = mp_if< mp_true, int, void> ; // int
using R2 = mp_if< mp_false, int, void> ; // void< / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 37. Using mp_if to fail substitution when a condition is not met< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using void_if_const = mp_if< std::is_const< T> , void> ;
template< class... T> using void_if_all_const =
mp_if< mp_all< std::is_const< T> ...> , void> ;
template< class T> using if_non_const = mp_if< mp_not< std::is_const< T> > , T> ;< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_eval_if_c_c_t_f_u" > mp_eval_if_c< C, T, F, U… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< bool C, class T, template< class...> class F, class... U> using mp_eval_if_c =
/*...*/;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_eval_if_c< C, T, F, U… ​ > < / code > is an alias for < code > T< / code > when < code > C< / code > is < code > true< / code > , for < code > F< U… ​ > < / code > otherwise. Its purpose
is to avoid evaluating < code > F< U… ​ > < / code > when the condition is < code > true< / code > as it may not be valid in this case.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 38. Using mp_eval_if_c to select the first pack element, or void< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class... T> using first_or_void =
mp_eval_if_c< sizeof...(T) == 0, void, mp_apply, mp_first, mp_list< T...> > ;< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_eval_if_c_t_f_u" > mp_eval_if< C, T, F, U… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class C, class T, template< class...> class F, class... U> using mp_eval_if =
mp_eval_if_c< static_cast< bool> (C::value), T, F, U...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Like < code > mp_eval_if_c< / code > , but the first argument is a type.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 39. Using mp_eval_if to select the first list element, or void< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class L> using first_or_void = mp_eval_if< mp_empty< L> , void, mp_first, L> ;< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_eval_if_q_c_t_q_u" > mp_eval_if_q< C, T, Q, U… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class C, class T, class Q, class... U> using mp_eval_if_q =
mp_eval_if< C, T, Q::template fn, U...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Like < code > mp_eval_if< / code > , but takes a quoted metafunction.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_valid_f_t" > mp_valid< F, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... T> using mp_valid = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_valid< F, T… ​ > < / code > is an alias for < code > mp_true< / code > when < code > F< T… ​ > < / code > is a valid expression, for < code > mp_false< / code > otherwise.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 40. Using mp_valid to write a metafunction that checks for the existence of a nested type< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using get_nested_type = typename T::type;
template< class T> struct has_nested_type: mp_valid< get_nested_type, T> {};< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_defer_f_t" > mp_defer< F, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... T> using mp_defer = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > When < code > mp_valid< F, T… ​ > < / code > is < code > mp_true< / code > , < code > mp_defer< F, T… ​ > < / code > is a struct with a nested type < code > type< / code > which is an alias for < code > F< T… ​ > < / code > . Otherwise,
< code > mp_defer< F, T… ​ > < / code > is an empty struct.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_quote_f" > mp_quote< F> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F> struct mp_quote
{
template< class... T> using fn = F< T...> ;
};< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_quote< F> < / code > transforms the template < code > F< / code > into a type with a nested template < code > fn< / code > such that < code > fn< T… ​ > < / code > returns < code > F< T… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 41. Using mp_quote to make a list of metafunctions< / div >
< div class = "content" >
< pre class = "highlight" > < code > using LQ = mp_list< mp_quote< std::is_const> , mp_quote< std::is_volatile> > ;< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_invoke_q_t" > mp_invoke< Q, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class Q, class... T> using mp_invoke = typename Q::template fn< T...> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_invoke< Q, T… ​ > < / code > evaluates the nested template < code > fn< / code > of a quoted metafunction. < code > mp_invoke< mp_quote< F> , T… ​ > < / code > returns < code > F< T… ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 42. Using mp_invoke to invoke a list of metafunctions, technique 1< / div >
< div class = "content" >
< pre class = "highlight" > < code > using LQ = mp_list< mp_quote< std::is_const> , mp_quote< std::is_volatile> > ;
template< class T> using is_const_and_volatile =
mp_all< mp_product< mp_invoke, LQ, mp_list< T> > > ;< / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 43. Using mp_invoke to invoke a list of metafunctions, technique 2< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using is_const_and_volatile =
mp_all< mp_transform_q< mp_bind_back< mp_invoke, T> , LQ> > ;< / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 44. Using mp_invoke to invoke a list of metafunctions, technique 3< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using is_const_and_volatile =
mp_all< mp_transform< mp_invoke, LQ, mp_fill< LQ, T> > > ;< / code > < / pre >
< / div >
< / div >
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< / div >
< / div >
< div class = "sect2" >
< h3 id = "algorithm" > Algorithms, < boost/mp11/algorithm.hpp> < / h3 >
< div class = "sect3" >
< h4 id = "mp_assign_l1_l2" > mp_assign< L1, L2> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L1, class L2> using mp_assign = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_assign< L1< T1… ​ > , L2< T2… ​ > > < / code > is an alias for < code > L1< T2… ​ > < / code > . That is, it replaces the elements of < code > L1< / code > with those of < code > L2< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 45. Using mp_assign with mp_list and std::tuple< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< long> ;
using L2 = mp_list< int, float> ;
using R1 = mp_assign< L1, L2> ; // std::tuple< int, float> < / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 46. Using mp_assign with mp_list and std::pair< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::pair< long, char> ;
using L2 = mp_list< int, float> ;
using R1 = mp_assign< L1, L2> ; // std::pair< int, float> < / code > < / pre >
< / div >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 1. mp_assign< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L2< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_assign< L1, L2> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_clear_l" > mp_clear< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_clear = mp_assign< L, mp_list< > > ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_clear< L< T… ​ > > < / code > is an alias for < code > L< > < / code > , that is, it removes the elements of < code > L< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 47. Using mp_clear with std::tuple< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< int, float> ;
using R1 = mp_clear< L1> ; // std::tuple< > < / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_transform_f_l" > mp_transform< F, L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... L> using mp_transform = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_transform< F, L1< T1… ​ > , L2< T2… ​ > , … ​ , Ln< Tn… ​ > > < / code > applies < code > F< / code > to each successive tuple of elements and returns < code > L1< F< T1, T2, … ​ , Tn> … ​ > < / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 48. Using mp_transform to produce a list of pointers from a list of pointees< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T> using add_pointer_t =
typename std::add_pointer< T> ::type; // std::add_pointer_t in C++14
using L1 = std::tuple< void, int, float> ;
using R1 = mp_transform< add_pointer_t, L1> ; // std::tuple< void*, int*, float*> < / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 49. Using mp_transform to compare the contents of two lists of types< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< void, int, float> ;
using L2 = mp_list< void, int, float> ;
using R1 = mp_all< mp_transform< std::is_same, L1, L2> > ; // mp_true< / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 50. Using mp_transform to compare the contents of two lists of integral constants< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class T1, class T2> using eq = mp_bool< T1::value == T2::value> ;
using L1 = std::tuple< mp_int< 1> , mp_int< 2> , mp_int< 3> > ;
using L2 = mp_list< mp_size_t< 1> , mp_size_t< 2> , mp_size_t< 3> > ;
using R1 = mp_all< mp_transform< eq, L1, L2> > ; // mp_true< / code > < / pre >
< / div >
< / div >
< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
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< caption class = "title" > Illustration 2. mp_transform on one list< / caption >
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< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
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< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_transform< F, L1> < / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 1< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 2< / sub > > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > n< / sub > > < / code > < / p > < / td >
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< / tr >
< / tbody >
< / table >
< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
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< caption class = "title" > Illustration 3. mp_transform on two lists< / caption >
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< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
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< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L2< / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > n< / sub > < / code > < / p > < / td >
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< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_transform< F, L1, L2> < / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 1< / sub > ,B< sub > 1< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 2< / sub > ,B< sub > 2< / sub > > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > n< / sub > ,B< sub > n< / sub > > < / code > < / p > < / td >
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< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_transform_q_q_l" > mp_transform_q< Q, L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class Q, class... L> using mp_transform_q =
mp_transform< Q::template fn, L...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > As < code > mp_transform< / code > , but takes a quoted metafunction.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 51. Using mp_transform_q to count the occurences of < code > void< / code > in a list< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< void, int, float, void, int> ;
using R1 = mp_apply< mp_plus,
mp_transform_q< mp_bind_front< std::is_same, void> , L1> > ; // mp_int< 2> < / code > < / pre >
< / div >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 4. mp_transform_q on two lists< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L2< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_transform_q< Q, L1, L2> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > Q::fn< A< sub > 1< / sub > ,B< sub > 1< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > Q::fn< A< sub > 2< / sub > ,B< sub > 2< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > Q::fn< A< sub > n< / sub > ,B< sub > n< / sub > > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_transform_if_p_f_l" > mp_transform_if< P, F, L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< template< class...> class P, template< class...> class F, class L...>
using mp_transform_if = /*...*/;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_transform_if< P, F, L1, L2, … ​ , Ln> < / code > replaces the elements of the list < code > L1< / code > for which < code > mp_to_bool< P< T1, T2, … ​ , Tn> > < / code > is < code > mp_true< / code > with
< code > F< T1, T2, … ​ , Tn> < / code > , and returns the result, where < code > Ti< / code > are the corresponding elements of < code > Li< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 52. Using mp_transform_if to replace the occurences of 'void' in a list with the corresponding elements of a second list< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< void, int, float, void, int> ;
using L2 = std::tuple< char[1], char[2], char[3], char[4], char[5]> ;
template< class T1, class T2> using first_is_void = std::is_same< T1, void> ;
template< class T1, class T2> using second = T2;
using R1 = mp_transform_if< first_is_void, second, L1, L2> ;
// std::tuple< char[1], int, float, char[4], int> < / code > < / pre >
< / div >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 5. mp_transform_if< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > P< A< sub > i< / sub > > < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_false< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_true< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_false< / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L2< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_transform_if< P, F, L1, L2> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 2< / sub > ,B< sub > 2< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
2017-06-07 00:02:25 +03:00
< / div >
< div class = "sect3" >
< h4 id = "mp_transform_if_q_qp_qf_l" > mp_transform_if_q< Qp, Qf, L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class Qp, class Qf, class... L> using mp_transform_if_q =
mp_transform_if< Qp::template fn, Qf::template fn, L...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
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< p > As < code > mp_transform_if< / code > , but takes quoted metafunctions.< / p >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 53. Using mp_transform_if_q to replace the occurences of 'void' in a list with the corresponding elements of a second list< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< void, int, float, void, int> ;
using L2 = std::tuple< char[1], char[2], char[3], char[4], char[5]> ;
using R1 = mp_transform_if_q< mp_bind< std::is_same, _1, void> , _2, L1, L2> ;
// std::tuple< char[1], int, float, char[4], int> < / code > < / pre >
< / div >
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< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 6. mp_transform_if_q< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > Qp::fn< A< sub > i< / sub > > < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_false< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_true< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_false< / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L2< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_transform_if_q< Qp, _2, L1, L2> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_fill_l_v" > mp_fill< L, V> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V> using mp_fill = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_fill< L< T… ​ > , V> < / code > returns < code > L< V, V, … ​ , V> < / code > , with the result having the same size as the input.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 54. Using mp_fill with std::tuple< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::tuple< void, int, float> ;
using R1 = mp_fill< L1, double> ; // std::tuple< double, double, double> < / code > < / pre >
< / div >
< / div >
< div class = "listingblock" >
< div class = "title" > Code Example 55. Using mp_fill with std::pair< / div >
< div class = "content" >
< pre class = "highlight" > < code > using L1 = std::pair< int, float> ;
using R1 = mp_fill< L1, void> ; // std::pair< void, void> < / code > < / pre >
< / div >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 7. mp_fill< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_fill< L1, V> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > V< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > V< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > V< / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_count_l_v" > mp_count< L, V> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V> using mp_count = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_count< L, V> < / code > returns < code > mp_size_t< N> < / code > , where < code > N< / code > is the number of elements of < code > L< / code > same as < code > V< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_count_if_l_p" > mp_count_if< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P> using mp_count_if = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_count_if< L, P> < / code > returns < code > mp_size_t< N> < / code > , where < code > N< / code > is the number of elements < code > T< / code > of < code > L< / code > for which < code > mp_to_bool< P< T> > < / code > is < code > mp_true< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_contains_l_v" > mp_contains< L, V> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V> using mp_contains = mp_to_bool< mp_count< L, V> > ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_contains< L, V> < / code > is < code > mp_true< / code > when < code > L< / code > contains an element < code > V< / code > , < code > mp_false< / code > otherwise.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_repeat_c_l_n" > mp_repeat_c< L, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, std::size_t N> using mp_repeat_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_repeat_c< L, N> < / code > returns a list of the same type as < code > L< / code > that consists of < code > N< / code > concatenated copies of < code > L< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_repeat_l_n" > mp_repeat< L, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class N> using mp_repeat = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_repeat_c< / code > but with a type argument < code > N< / code > . The number of copies is < code > N::value< / code > and must be nonnegative.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_product_f_l" > mp_product< F, L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... L> using mp_product = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_product< F, L1< T1… ​ > , L2< T2… ​ > , … ​ , Ln< Tn… ​ > > < / code > evaluates < code > F< U1, U2, … ​ , Un> < / code > for values < code > Ui< / code > taken from
the Cartesian product of the lists, as if the elements < code > Ui< / code > are formed by < code > n< / code > nested loops, each traversing < code > Li< / code > .
It returns a list of type < code > L1< / code > containing the results of the application of < code > F< / code > .< / p >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
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< caption class = "title" > Illustration 8. mp_product on two lists< / caption >
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< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
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< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L2< / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > 2< / sub > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > B< sub > m< / sub > < / code > < / p > < / td >
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< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_product< F, L1, L2> < / strong > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 1< / sub > ,B< sub > 1< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 1< / sub > ,B< sub > 2< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 1< / sub > ,B< sub > m< / sub > > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 2< / sub > ,B< sub > 1< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 2< / sub > ,B< sub > 2< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > 2< / sub > ,B< sub > m< / sub > > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < / td >
< td class = "tableblock halign-center valign-middle" colspan = "4" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > n< / sub > ,B< sub > 1< / sub > > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > n< / sub > ,B< sub > 2< / sub > > < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
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< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > F< A< sub > n< / sub > ,B< sub > m< / sub > > < / code > < / p > < / td >
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< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_product_q_q_l" > mp_product_q< Q, L… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class Q, class... L> using mp_product_q = mp_product< Q::template fn, L...> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > As < code > mp_product< / code > , but takes a quoted metafunction.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_drop_c_l_n" > mp_drop_c< L, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, std::size_t N> using mp_drop_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_drop_c< L, N> < / code > removes the first < code > N< / code > elements of < code > L< / code > and returns the result.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_drop_l_n" > mp_drop< L, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class N> using mp_drop = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_drop_c< / code > , but with a type argument < code > N< / code > . < code > N::value< / code > must be a nonnegative number.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_iota_c_n" > mp_iota_c< N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< std::size_t N> using mp_iota_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_iota_c< N> < / code > is an alias for < code > mp_list< mp_size_t< 0> , mp_size_t< 1> , … ​ , mp_size_t< N-1> > < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_iota_n" > mp_iota< N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class N> using mp_iota = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_iota_c< / code > , but with a type argument < code > N< / code > . < code > N::value< / code > must be a nonnegative number. Returns
< code > mp_list< std::integral_constant< T, 0> , std::integral_constant< T, 1> , … ​ , std::integral_constant< T, N::value-1> > < / code >
where < code > T< / code > is the type of < code > N::value< / code > .< / p >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 9. mp_iota< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_iota< mp_int< 4> > < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_int< 0> < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_int< 1> < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_int< 2> < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_int< 3> < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_at_c_l_i" > mp_at_c< L, I> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, std::size_t I> using mp_at_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
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< p > < code > mp_at_c< L, I> < / code > returns the < code > I< / code > -th element of < code > L< / code > , zero-based.< / p >
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< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_at_l_i" > mp_at< L, I> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class I> using mp_at = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_at_c< / code > , but with a type argument < code > I< / code > . < code > I::value< / code > must be a nonnegative number.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_take_c_l_n" > mp_take_c< L, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, std::size_t N> using mp_take_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_take_c< L, N> < / code > returns a list of the same type as < code > L< / code > containing the first < code > N< / code > elements of < code > L< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_take_l_n" > mp_take< L, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class N> using mp_take = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_take_c< / code > , but with a type argument < code > N< / code > . < code > N::value< / code > must be a nonnegative number.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_insert_c_l_i_t" > mp_insert_c< L, I, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, std::size_t I, class... T> using mp_insert_c =
mp_append< mp_take_c< L, I> , mp_push_front< mp_drop_c< L, I> , T...> > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Inserts the elements < code > T… ​ < / code > into the list < code > L< / code > at position < code > I< / code > (a zero-based index).< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_insert_l_i_t" > mp_insert< L, I, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, class I, class... T> using mp_insert =
mp_append< mp_take< L, I> , mp_push_front< mp_drop< L, I> , T...> > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_insert_c< / code > , but with a type argument < code > I< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_erase_c_l_i_j" > mp_erase_c< L, I, J> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, std::size_t I, std::size_t J> using mp_erase_c =
mp_append< mp_take_c< L, I> , mp_drop_c< L, J> > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Removes from the list < code > L< / code > the elements with indices from < code > I< / code > (inclusive) to < code > J< / code > (exclusive).< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_erase_l_i_j" > mp_erase< L, I, J> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, class I, class J> using mp_erase =
mp_append< mp_take< L, I> , mp_drop< L, J> > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_erase_c< / code > , but with a type arguments < code > I< / code > and < code > J< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_replace_l_v_w" > mp_replace< L, V, W> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V, class W> using mp_replace = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Replaces all < code > V< / code > elements of < code > L< / code > with < code > W< / code > and returns the result.< / p >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 10. mp_replace< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > V< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_replace< L1, V, W> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > W< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_replace_if_l_p_w" > mp_replace_if< L, P, W> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P, class W> using mp_replace_if = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Replaces all < code > T< / code > elements of < code > L< / code > for which < code > mp_to_bool< P< T> > < / code > is < code > mp_true< / code > with < code > W< / code > and returns the result.< / p >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 11. mp_replace_if< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > P< A< sub > i< / sub > > < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_false< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_true< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > mp_false< / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_replace_if< L1, P, W> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > W< / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_replace_at_c_l_i_w" > mp_replace_at_c< L, I, W> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, std::size_t I, class W> using mp_replace_at_c = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Replaces the element of < code > L< / code > at zero-based index < code > I< / code > with < code > W< / code > and returns the result.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_replace_at_l_i_w" > mp_replace_at< L, I, W> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class I, class W> using mp_replace_at = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > mp_replace_at_c< / code > , but with a type argument < code > I< / code > . < code > I::value< / code > must be a nonnegative number.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_copy_if_l_p" > mp_copy_if< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P> using mp_copy_if = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Copies the elements < code > T< / code > of < code > L< / code > for which < code > mp_to_bool< P< T> > < / code > is < code > mp_true< / code > to a new list of the same type and returns it.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_remove_l_v" > mp_remove< L, V> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V> using mp_remove = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Removes all < code > V< / code > elements of < code > L< / code > and returns the result.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_remove_if_l_p" > mp_remove_if< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P> using mp_remove_if = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Removes all elements < code > T< / code > of < code > L< / code > for which < code > mp_to_bool< P< T> > < / code > is < code > mp_true< / code > and returns the result.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_partition_l_p" > mp_partition< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P> using mp_partition = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_partition< L< T… ​ > , P> < / code > partitions < code > L< / code > into two lists < code > L< U1… ​ > < / code > and < code > L< U2… ​ > < / code > such that < code > mp_to_bool< P< T> > < / code > is < code > mp_true< / code >
for the elements of < code > L< U1… ​ > < / code > and < code > mp_false< / code > for the elements of < code > L< U2… ​ > < / code > . Returns < code > L< L< U1… ​ > , L< U2… ​ > > < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_sort_l_p" > mp_sort< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P> using mp_sort = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_sort< L, P> < / code > sorts the list < code > L< / code > according to the strict weak ordering < code > mp_to_bool< P< T, U> > < / code > .< / p >
< / div >
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< div class = "listingblock" >
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< div class = "title" > Code Example 56. Using mp_sort to sort a list of std::ratio values< / div >
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< div class = "content" >
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< pre > #include < ratio>
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using L1 = mp_list< std::ratio< 1,2> , std::ratio< 1,4> > ;
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using R1 = mp_sort< L1, std::ratio_less> ; // mp_list< ratio< 1,4> , ratio< 1,2> > < / pre >
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< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_find_l_v" > mp_find< L, V> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V> using mp_find = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_find< L, V> < / code > returns the index at which the type < code > V< / code > is located in the list < code > L< / code > . It’ s an alias for < code > mp_size_t< I> < / code > ,
where < code > I< / code > is the zero-based index of the first occurence of < code > V< / code > in < code > L< / code > . If < code > L< / code > does not contain < code > V< / code > , < code > mp_find< L, V> < / code >
is < code > mp_size< L> < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_find_if_l_p" > mp_find_if< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, template< class...> class P> using mp_find_if = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_find_f< L, P> < / code > is an alias for < code > mp_size_t< I> < / code > , where < code > I< / code > is the zero-based index of the first element < code > T< / code > in < code > L< / code > for which
< code > mp_to_bool< P< T> > < / code > is < code > mp_true< / code > . If there is no such element, < code > mp_find_if< L, P> < / code > is < code > mp_size< L> < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_reverse_l" > mp_reverse< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_reverse = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_reverse< L< T1, T2, … ​ , Tn> > < / code > is < code > L< Tn, … ​ , T2, T1> < / code > .< / p >
< / div >
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< table class = "tableblock frame-all grid-all" style = "width: 85%;" >
< caption class = "title" > Illustration 12. mp_reverse< / caption >
< colgroup >
< col style = "width: 50%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< col style = "width: 12.5%;" >
< / colgroup >
< tbody >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > L1< / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 2< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" colspan = "5" > < / td >
< / tr >
< tr >
< td class = "tableblock halign-left valign-middle" > < p class = "tableblock" > < code > < strong > mp_reverse< L1> < / strong > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > n-1< / sub > < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > … ​ < / code > < / p > < / td >
< td class = "tableblock halign-center valign-middle" > < p class = "tableblock" > < code > A< sub > 1< / sub > < / code > < / p > < / td >
< / tr >
< / tbody >
< / table >
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< / div >
< div class = "sect3" >
< h4 id = "mp_fold_l_v_f" > mp_fold< L, V, F> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class V, template< class...> class F> using mp_fold = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_fold< L< T1, T2, … ​ , Tn> , V, F> < / code > is < code > F< F< F< F< V, T1> , T2> , … ​ > , Tn> < / code > , or < code > V< / code > , if < code > L< / code > is empty.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_reverse_fold_l_v_f" > mp_reverse_fold< L, V, F> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, class V, template< class...> class F> using mp_reverse_fold =
/*...*/;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_reverse_fold< L< T1, T2, … ​ , Tn> , V, F> < / code > is < code > F< T1, F< T2, F< … ​ , F< Tn, V> > > > < / code > , or < code > V< / code > , if < code > L< / code > is empty.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_unique_l" > mp_unique< L> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L> using mp_unique = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_unique< L> < / code > returns a list of the same type as < code > L< / code > with the duplicate elements removed.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_all_of_l_p" > mp_all_of< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, template< class...> class P> using mp_all_of =
mp_bool< mp_count_if< L, P> ::value == mp_size< L> ::value > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_all_of< L, P> < / code > is < code > mp_true< / code > when < code > P< / code > holds for all elements of < code > L< / code > , < code > mp_false< / code > otherwise. When < code > L< / code > is empty, the result is < code > mp_true< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_none_of_l_p" > mp_none_of< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, template< class...> class P> using mp_none_of =
mp_bool< mp_count_if< L, P> ::value == 0 > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_none_of< L, P> < / code > is < code > mp_true< / code > when < code > P< / code > holds for no element of < code > L< / code > , < code > mp_false< / code > otherwise. When < code > L< / code > is empty, the result is < code > mp_true< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_any_of_l_p" > mp_any_of< L, P> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class L, template< class...> class P> using mp_any_of =
mp_bool< mp_count_if< L, P> ::value != 0 > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_any_of< L, P> < / code > is < code > mp_true< / code > when < code > P< / code > holds for at least one element of < code > L< / code > , < code > mp_false< / code > otherwise. When < code > L< / code > is empty, the result is < code > mp_false< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_for_each_l_f" > mp_for_each< L> (f)< / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class L, class F> constexpr F mp_for_each(F& & f);< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_for_each< L> (f)< / code > calls < code > f< / code > with < code > T()< / code > for each element < code > T< / code > of the list < code > L< / code > , in order.< / p >
< / div >
< div class = "paragraph" >
< p > Returns < code > std::forward< F> (f)< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 57. Using mp_for_each and a C++14 lambda to print a tuple< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class... T> void print( std::tuple< T...> const & tp )
{
std::size_t const N = sizeof...(T);
mp_for_each< mp_iota_c< N> > ( []( auto I ){
// I is mp_size_t< 0> , mp_size_t< 1> , ..., mp_size_t< N-1>
std::cout < < std::get< I> (tp) < < std::endl;
});
}< / code > < / pre >
< / div >
< / div >
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< / div >
< div class = "sect3" >
< h4 id = "mp_with_index_n_i_f" > mp_with_index< N> (i, f)< / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< std::size_t N, class F>
constexpr auto mp_with_index( std::size_t i, F & & f )
-> decltype(std::declval< F> ()(std::declval< mp_size_t< 0> > ()));< / pre >
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< / div >
< / div >
< div class = "paragraph" >
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< p > < code > mp_with_index< N> (i, f)< / code > calls < code > f< / code > with < code > mp_size_t< i> ()< / code > and returns the result. < code > i< / code > must be less than < code > N< / code > .
Only < code > constexpr< / code > on C++14 and higher.< / p >
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< / div >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class N, class F>
constexpr auto mp_with_index( std::size_t i, F & & f )
-> decltype(std::declval< F> ()(std::declval< mp_size_t< 0> > ()));< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Returns < code > mp_with_index< N::value> (i, f)< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 58. Using mp_with_index and a C++14 lambda to print the active element of a variant< / div >
< div class = "content" >
< pre class = "highlight" > < code > template< class... T> void print( std::variant< T...> const& v )
{
mp_with_index< sizeof...(T)> ( v.index(), [& ]( auto I ) {
// I is mp_size_t< v.index()> here
std::cout < < std::get< I> ( v ) < < std::endl;
});
}< / code > < / pre >
< / div >
< / div >
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< / div >
< / div >
< div class = "sect2" >
< h3 id = "set" > Set Operations, < boost/mp11/set.hpp> < / h3 >
< div class = "paragraph" >
< p > A set is a list whose elements are unique.< / p >
< / div >
< div class = "sect3" >
< h4 id = "mp_set_contains_s_v" > mp_set_contains< S, V> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class S, class V> using mp_set_contains = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_set_contains< S, V> < / code > is < code > mp_true< / code > if the type < code > V< / code > is an element of the set < code > S< / code > , < code > mp_false< / code > otherwise.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_set_push_back_s_t" > mp_set_push_back< S, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class S, class... T> using mp_set_push_back = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > For each < code > T1< / code > in < code > T… ​ < / code > , < code > mp_set_push_back< S, T… ​ > < / code > appends < code > T1< / code > to the end of < code > S< / code > if it’ s not already an element of < code > S< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_set_push_front_s_t" > mp_set_push_front< S, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class S, class... T> using mp_set_push_front = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_set_push_front< S, T… ​ > < / code > inserts at the front of < code > S< / code > those elements of < code > T… ​ < / code > for which < code > S< / code > does not already contain the same type.< / p >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "map" > Map Operations, < boost/mp11/map.hpp> < / h3 >
< div class = "paragraph" >
< p > A map is a list of lists, the inner lists having at least one element (the key.) The keys of the map must be unique.< / p >
< / div >
< div class = "sect3" >
< h4 id = "mp_map_find_m_k" > mp_map_find< M, K> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class M, class K> using mp_map_find = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_map_find< M, K> < / code > is an alias for the element of the map < code > M< / code > with a key < code > K< / code > , or for < code > void< / code > , if there is no such element.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_map_contains_m_k" > mp_map_contains< M, K> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class M, class K> using mp_map_contains =
mp_not< std::is_same< mp_map_find< M, K> , void> > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_map_contains< M, K> < / code > is < code > mp_true< / code > if the map < code > M< / code > contains an element with a key < code > K< / code > , < code > mp_false< / code > otherwise.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_map_insert_m_t" > mp_map_insert< M, T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class M, class T> using mp_map_insert =
mp_if< mp_map_contains< M, mp_first< T> > , M, mp_push_back< M, T> > ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > Inserts the element < code > T< / code > into the map < code > M< / code > , if an element with a key < code > mp_first< T> < / code > is not already in < code > M< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_map_replace_m_t" > mp_map_replace< M, T> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class M, class T> using mp_map_replace = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > If the map < code > M< / code > does not contain an element with a key < code > mp_first< T> < / code > , inserts it (using < code > mp_push_back< M, T> < / code > ); otherwise,
replaces the existing element with < code > T< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_map_update_m_t_f" > mp_map_update< M, T, F> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class M, class T, template< class...> class F> using mp_map_update = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > If the map < code > M< / code > does not contain an element with a key < code > mp_first< T> < / code > , inserts it (using < code > mp_push_back< M, T> < / code > ); otherwise,
replaces the existing element < code > L< X, Y… ​ > < / code > with < code > L< X, F< X, Y… ​ > > < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_map_erase_m_k" > mp_map_erase< M, K> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class M, class K> using mp_map_erase = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > If the map < code > M< / code > contains an element with a key < code > K< / code > , removes it.< / p >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "function" > Helper Metafunctions, < boost/mp11/function.hpp> < / h3 >
< div class = "sect3" >
< h4 id = "mp_void_t" > mp_void< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_void = void;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > Same as < code > std::void_t< / code > from C++17.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_and_t" > mp_and< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_and = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_and< T… ​ > < / code > applies < code > mp_to_bool< / code > to the types in < code > T… ​ < / code > , in order. If the result of an application is < code > mp_false< / code > , < code > mp_and< / code >
returns < code > mp_false< / code > . If the application causes a substitution failure, returns < code > mp_false< / code > . If all results are < code > mp_true< / code > ,
returns < code > mp_true< / code > . < code > mp_and< > < / code > is < code > mp_true< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 59. mp_and behavior< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using R1 = mp_and< mp_true, mp_true> ; // mp_true
using R2 = mp_and< mp_false, void> ; // mp_false, void is not reached
using R3 = mp_and< mp_false, mp_false> ; // mp_false
using R4 = mp_and< void, mp_true> ; // mp_false (!)< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_all_t" > mp_all< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_all = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_all< T… ​ > < / code > is < code > mp_true< / code > if < code > mp_to_bool< U> < / code > is < code > mp_true< / code > for all types < code > U< / code > in < code > T… ​ < / code > , < code > mp_false< / code > otherwise. Same as
< code > mp_and< / code > , but does not perform short-circuit evaluation. < code > mp_and< mp_false, void> < / code > is < code > mp_false< / code > , but < code > mp_all< mp_false, void> < / code >
is an error because < code > void< / code > does not have a nested < code > value< / code > . The upside is that < code > mp_all< / code > is potentially faster and does not
mask substitution failures as < code > mp_and< / code > does.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 60. mp_all behavior< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using R1 = mp_all< mp_true, mp_true> ; // mp_true
using R2 = mp_all< mp_false, void> ; // compile-time error
using R3 = mp_all< mp_false, mp_false> ; // mp_false
using R4 = mp_all< void, mp_true> ; // compile-time error< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_or_t" > mp_or< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_or = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_or< T… ​ > < / code > applies < code > mp_to_bool< / code > to the types in < code > T… ​ < / code > , in order. If the result of an application is < code > mp_true< / code > , < code > mp_or< / code >
returns < code > mp_true< / code > . If all results are < code > mp_false< / code > , returns < code > mp_false< / code > . < code > mp_or< > < / code > is < code > mp_false< / code > .< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 61. mp_or behavior< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using R1 = mp_or< mp_true, mp_false> ; // mp_true
using R2 = mp_or< mp_true, void> ; // mp_true, void is not reached
using R3 = mp_or< mp_false, mp_false> ; // mp_false
using R4 = mp_or< void, mp_true> ; // compile-time error< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_any_t" > mp_any< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_any = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_any< T… ​ > < / code > is < code > mp_true< / code > if < code > mp_to_bool< U> < / code > is < code > mp_true< / code > for any type < code > U< / code > in < code > T… ​ < / code > , < code > mp_false< / code > otherwise. Same as
< code > mp_or< / code > , but does not perform short-circuit evaluation.< / p >
< / div >
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< div class = "listingblock" >
< div class = "title" > Code Example 62. mp_any behavior< / div >
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< div class = "content" >
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< pre class = "highlight" > < code > using R1 = mp_any< mp_true, mp_false> ; // mp_true
using R2 = mp_any< mp_true, void> ; // compile-time error
using R3 = mp_any< mp_false, mp_false> ; // mp_false
using R4 = mp_any< void, mp_true> ; // compile-time error< / code > < / pre >
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< / div >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_same_t" > mp_same< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_same = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_same< T… ​ > < / code > is < code > mp_true< / code > if all the types in < code > T… ​ < / code > are the same type, < code > mp_false< / code > otherwise. < code > mp_same< > < / code > is < code > mp_true< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_plus_t" > mp_plus< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class... T> using mp_plus = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_plus< T… ​ > < / code > is an integral constant type with a value that is the sum of < code > U::value< / code > for all types < code > U< / code > in < code > T… ​ < / code > .
< code > mp_plus< > < / code > is < code > mp_int< 0> < / code > .< / p >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "bind" > Bind, < boost/mp11/bind.hpp> < / h3 >
< div class = "sect3" >
< h4 id = "mp_arg_i" > mp_arg< I> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< std::size_t I> struct mp_arg;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_arg< I> < / code > is a quoted metafunction whose nested template < code > fn< T… ​ > < / code > returns the < code > I< / code > -th zero-based element of < code > T… ​ < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "1_9" > _1, … ​ , _9< / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > using _1 = mp_arg< 0> ;
using _2 = mp_arg< 1> ;
using _3 = mp_arg< 2> ;
using _4 = mp_arg< 3> ;
using _5 = mp_arg< 4> ;
using _6 = mp_arg< 5> ;
using _7 = mp_arg< 6> ;
using _8 = mp_arg< 7> ;
using _9 = mp_arg< 8> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > _1< / code > to < code > _9< / code > are placeholder types, the equivalent to the placeholders of < code > boost::bind< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_bind_f_t" > mp_bind< F, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... T> struct mp_bind;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_bind< F, T… ​ > < / code > is a quoted metafunction that implements the type-based equivalent of < code > boost::bind< / code > . Its nested
template < code > fn< U… ​ > < / code > returns < code > F< V… ​ > < / code > , where < code > V… ​ < / code > is < code > T… ​ < / code > with the placeholders replaced by the corresponding element
of < code > U… ​ < / code > and the < code > mp_bind< / code > expressions replaced with their corresponding evaluations against < code > U… ​ < / code > .< / p >
< / div >
< div class = "paragraph" >
< p > For example, < code > mp_bind< F, int, _2, mp_bind< G, _1> > ::fn< float, void> < / code > is < code > F< int, void, G< float> > < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_bind_q_q_t" > mp_bind_q< Q, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class Q, class... T> using mp_bind_q = mp_bind< Q::template fn, T...> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > As < code > mp_bind< / code > , but takes a quoted metafunction.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_bind_front_f_t" > mp_bind_front< F, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... T> struct mp_bind_front;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_bind_front< F, T… ​ > < / code > binds the leftmost arguments of < code > F< / code > to < code > T… ​ < / code > . Its nested template < code > fn< U… ​ > < / code > returns < code > F< T… ​ , U… ​ > < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_bind_front_q_q_t" > mp_bind_front_q< Q, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class Q, class... T> using mp_bind_front_q =
mp_bind_front< Q::template fn, T...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > As < code > mp_bind_front< / code > , but takes a quoted metafunction.< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_bind_back_f_t" > mp_bind_back< F, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< template< class...> class F, class... T> struct mp_bind_back;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > mp_bind_back< F, T… ​ > < / code > binds the rightmost arguments of < code > F< / code > to < code > T… ​ < / code > . Its nested template < code > fn< U… ​ > < / code > returns < code > F< U… ​ , T… ​ > < / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "mp_bind_back_q_q_t" > mp_bind_back_q< Q, T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class Q, class... T> using mp_bind_back_q =
mp_bind_back< Q::template fn, T...> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > As < code > mp_bind_back< / code > , but takes a quoted metafunction.< / p >
< / div >
< / div >
< / div >
< div class = "sect2" >
< h3 id = "integer_sequence" > Integer Sequences, < boost/mp11/integer_sequence.hpp> < / h3 >
< div class = "sect3" >
< h4 id = "integer_sequence_t_i" > integer_sequence< T, I… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T, T... I> struct integer_sequence
{
};< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > integer_sequence< T, I… ​ > < / code > holds a sequence of integers of type < code > T< / code > . Same as C++14’ s < code > std::integer_sequence< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "make_integer_sequence_t_n" > make_integer_sequence< T, N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class T, T N> using make_integer_sequence = /*...*/;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > make_integer_sequence< T, N> < / code > is < code > integer_sequence< T, 0, 1, … ​ , N-1> < / code > . Same as C++14’ s < code > std::make_integer_sequence< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "index_sequence_i" > index_sequence< I… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< std::size_t... I> using index_sequence = integer_sequence< std::size_t, I...> ;< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > index_sequence< I… ​ > < / code > is an alias for < code > integer_sequence< size_t, I… ​ > < / code > . Same as C++14’ s < code > std::index_sequence< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "make_index_sequence_n" > make_index_sequence< N> < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< std::size_t N> using make_index_sequence =
make_integer_sequence< std::size_t, N> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > make_index_sequence< N> < / code > is < code > index_sequence< 0, 1, … ​ , N-1> < / code > . Same as C++14’ s < code > std::make_index_sequence< / code > .< / p >
< / div >
< / div >
< div class = "sect3" >
< h4 id = "index_sequence_for_t" > index_sequence_for< T… ​ > < / h4 >
< div class = "literalblock" >
< div class = "content" >
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< pre > template< class... T> using index_sequence_for =
make_integer_sequence< std::size_t, sizeof...(T)> ;< / pre >
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< / div >
< / div >
< div class = "paragraph" >
< p > < code > index_sequence_for< N> < / code > is < code > make_index_sequence< sizeof… ​ (T)> < / code > . Same as C++14’ s < code > std::index_sequence_for< / code > .< / p >
< / div >
< / div >
< / div >
< div class = "sect2" >
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< h3 id = "tuple" > Tuple Operations, < boost/mp11/tuple.hpp> < / h3 >
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< div class = "sect3" >
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< h4 id = "tuple_apply_f_tp" > tuple_apply(f, tp)< / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class F, class Tp> constexpr /*...*/ tuple_apply(F& & f, Tp& & tp);< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > tuple_apply(f, tp)< / code > returns < code > std::forward< F> (f)(std::get< J> (std::forward< Tp> (tp))… ​ )< / code > for < code > J< / code > in 0..< code > N-1< / code > ,
where < code > N< / code > is < code > std::tuple_size< typename std::remove_reference< Tp> ::type> ::value< / code > . Same as < code > std::apply< / code > in C++17.< / p >
< / div >
< / div >
< div class = "sect3" >
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< h4 id = "construct_from_tuple_t_tp" > construct_from_tuple< T> (tp)< / h4 >
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< div class = "literalblock" >
< div class = "content" >
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< pre > template< class T, class Tp> T construct_from_tuple(Tp& & tp);< / pre >
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< / div >
< / div >
< div class = "paragraph" >
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< p > < code > construct_from_tuple< T> (tp)< / code > returns < code > T(std::get< J> (std::forward< Tp> (tp))… ​ )< / code > for < code > J< / code > in 0..< code > N-1< / code > ,
where < code > N< / code > is < code > std::tuple_size< typename std::remove_reference< Tp> ::type> ::value< / code > . Same as < code > std::make_from_tuple< / code > in C++17.
The name of the function doesn’ t match the C++17 one to avoid ambiguities when both are visible or in unqualified calls.< / p >
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< / div >
< / div >
< div class = "sect3" >
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< h4 id = "tuple_for_each_tp_f" > tuple_for_each(tp, f)< / h4 >
< div class = "literalblock" >
< div class = "content" >
< pre > template< class Tp, class F> constexpr F tuple_for_each(Tp& & tp, F& & f);< / pre >
< / div >
< / div >
< div class = "paragraph" >
< p > < code > tuple_for_each(tp, f)< / code > applies the function object < code > f< / code > to each element of < code > tp< / code > by evaluating the
expression < code > f(std::get< J> (std::forward< Tp> (tp)))< / code > for < code > J< / code > in 0..< code > N-1< / code > , where < code > N< / code > is < code > std::tuple_size< typename std::remove_reference< Tp> ::type> ::value< / code > .< / p >
< / div >
< div class = "paragraph" >
< p > Returns < code > std::forward< F> (f)< / code > .< / p >
< / div >
< / div >
< / div >
< / div >
< / div >
< div class = "sect1" >
< h2 id = "copyright_and_license" > Appendix A: Copyright and License< / h2 >
< div class = "sectionbody" >
< div class = "paragraph" >
< p > This documentation is< / p >
< / div >
< div class = "ulist" >
< ul >
< li >
< p > Copyright 2017 Peter Dimov< / p >
< / li >
< li >
< p > Distributed under the < a href = "http://www.boost.org/LICENSE_1_0.txt" > Boost Software License, Version 1.0< / a > .< / p >
< / li >
< / ul >
< / div >
< / div >
< / div >
< / div >
< div id = "footer" >
< div id = "footer-text" >
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Last updated 2017-06-11 03:50:25 GTBDT
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table tr.even, table tr.alt, table tr:nth-of-type(even) { background: none; }
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