boost_mp11/doc/mp11/definitions.qbk

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 /  Copyright 2017 Peter Dimov
 /
 / Distributed under the Boost Software License, Version 1.0. (See
 / accompanying file LICENSE_1_0.txt or copy at
 / http://www.boost.org/LICENSE_1_0.txt)
 /]

[section:definitions Definitions]

A /list/ is a '''—''' usually but not necessarily variadic '''—''' template class whose parameters are all types,
for example `mp_list<char[], void>`, `mp_list<>`, `std::tuple<int, float, char>`, `std::pair<int, float>`, `std::shared_ptr<X>`.

A /metafunction/ is a class template or a template alias whose parameters are all types, for example `std::add_pointer_t`,
`std::is_const`, `mp_second`, `mp_push_front`, `mp_list`, `std::tuple`, `std::pair`, `std::shared_ptr`, or

  template<class...> using F1 = void;
  template<class T> using F2 = T*;
  template<class... T> using F3 = std::integral_constant<std::size_t, sizeof...(T)>;

A /quoted metafunction/ is a class with a public metafunction member called `fn`, for example

  struct Q1 { template<class...> using fn = void; };
  struct Q2 { template<class T> using fn = T*; };
  struct Q3 { template<class... T> using fn = std::integral_constant<std::size_t, sizeof...(T)>; };

An /integral constant type/ is a class with a public member `value` that is an integral constant in the C++ sense. For example,
`std::integral_constant<int, 7>`, or

  struct N { static int constexpr value = 2; };

A /set/ is a list whose elements are unique.

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. For example,

  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]>>;

[endsect:definitions]