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Add support for n-ary functions to mp_compose

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Dmitry Arkhipov
2021-07-26 21:10:05 +03:00
parent 8cd25cc950
commit f4b3414e62
3 changed files with 19 additions and 4 deletions
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2
doc/mp11/utility.adoc
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@@ -295,7 +295,7 @@ As `mp_not_fn`, but takes a quoted metafunction.
`mp_compose<F1, F2, ..., Fn>` is a quoted metafunction that applies
`F1`, `F2`, ..., `Fn` to its argument, in sequence. That is,
`mp_compose<F1, F2, ..., Fn>::fn<T>` is `Fn<...F2<F1<T>>...>`.
`mp_compose<F1, F2, ..., Fn>::fn<T...>` is `Fn<...F2<F1<T...>>...>`.
## mp_compose_q<Q...>

8
include/boost/mp11/utility.hpp
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@@ -11,6 +11,8 @@
#include <boost/mp11/integral.hpp>
#include <boost/mp11/detail/mp_list.hpp>
#include <boost/mp11/detail/mp_fold.hpp>
#include <boost/mp11/detail/mp_front.hpp>
#include <boost/mp11/detail/mp_rename.hpp>
#include <boost/mp11/detail/config.hpp>
namespace boost
@@ -233,7 +235,7 @@ template<class Q> using mp_not_fn_q = mp_not_fn<Q::template fn>;
namespace detail
{
template<class T, class Q> using mp_reverse_invoke_q = mp_invoke_q<Q, T>;
template<class L, class Q> using mp_compose_helper = mp_list< mp_apply_q<Q, L> >;
} // namespace detail
@@ -241,14 +243,14 @@ template<class T, class Q> using mp_reverse_invoke_q = mp_invoke_q<Q, T>;
template<template<class...> class... F> struct mp_compose
{
template<class T> using fn = mp_fold<mp_list<mp_quote<F>...>, T, detail::mp_reverse_invoke_q>;
template<class... T> using fn = mp_front< mp_fold<mp_list<mp_quote<F>...>, mp_list<T...>, detail::mp_compose_helper> >;
};
#endif
template<class... Q> struct mp_compose_q
{
template<class T> using fn = mp_fold<mp_list<Q...>, T, detail::mp_reverse_invoke_q>;
template<class... T> using fn = mp_front< mp_fold<mp_list<Q...>, mp_list<T...>, detail::mp_compose_helper> >;
};
} // namespace mp11

13
test/mp_compose.cpp
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@@ -4,6 +4,7 @@
// https://www.boost.org/LICENSE_1_0.txt
#include <boost/mp11/list.hpp>
#include <boost/mp11/utility.hpp>
#include <boost/core/lightweight_test_trait.hpp>
@@ -15,6 +16,8 @@ template<class T> using G1 = F1<T>;
template<class T> using G2 = F2<T>;
template<class T> using G3 = F3<T>;
template<class... T> struct H {};
int main()
{
using namespace boost::mp11;
@@ -32,6 +35,10 @@ int main()
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose<F1, F2, F3>::fn<void>, F3<F2<F1<void>>>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose<G1, G2, G3>::fn<void>, F3<F2<F1<void>>>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose<H>::fn<int, char>, H<int, char>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose<H, F1>::fn<void, float>, F1<H<void, float>>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose<H, F1, G1>::fn<void, float>, G1<F1<H<void, float>>>>));
#endif
using QF1 = mp_quote<F1>;
@@ -42,6 +49,8 @@ int main()
using QG2 = mp_quote<G2>;
using QG3 = mp_quote<G3>;
using QH = mp_quote<H>;
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<>::fn<void>, void>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<QF1>::fn<void>, F1<void>>));
@@ -53,6 +62,10 @@ int main()
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<QF1, QF2, QF3>::fn<void>, F3<F2<F1<void>>>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<QG1, QG2, QG3>::fn<void>, F3<F2<F1<void>>>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<QH>::fn<int, char>, H<int, char>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<QH, QF1>::fn<void, float>, F1<H<void, float>>>));
BOOST_TEST_TRAIT_TRUE((std::is_same<mp_compose_q<QH, QF1, QG1>::fn<void, float>, G1<F1<H<void, float>>>>));
//
return boost::report_errors();