ceph/src/boost/boost/hof/match.hpp

   1 /*=============================================================================
   2     Copyright (c) 2012 Paul Fultz II
   3     match.h
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7
   8 #ifndef BOOST_HOF_GUARD_FUNCTION_OVERLOAD_H
   9 #define BOOST_HOF_GUARD_FUNCTION_OVERLOAD_H
  10
  11 /// match
  12 /// =====
  13 ///
  14 /// Description
  15 /// -----------
  16 ///
  17 /// The `match` function adaptor combines several functions together and
  18 /// resolves which one should be called by using C++ overload resolution. This
  19 /// is different than the [`first_of`](/include/boost/hof/conditional) adaptor which resolves
  20 /// them based on order.
  21 ///
  22 /// Synopsis
  23 /// --------
  24 ///
  25 ///     template<class... Fs>
  26 ///     constexpr match_adaptor<Fs...> match(Fs...fs);
  27 ///
  28 /// Requirements
  29 /// ------------
  30 ///
  31 /// Fs must be:
  32 ///
  33 /// * [ConstInvocable](ConstInvocable)
  34 /// * MoveConstructible
  35 ///
  36 /// Example
  37 /// -------
  38 ///
  39 ///     #include <boost/hof.hpp>
  40 ///     using namespace boost::hof;
  41 ///
  42 ///     struct int_class
  43 ///     {
  44 ///         int operator()(int) const
  45 ///         {
  46 ///             return 1;
  47 ///         }
  48 ///     };
  49 ///
  50 ///     struct foo
  51 ///     {};
  52 ///
  53 ///     struct foo_class
  54 ///     {
  55 ///         foo operator()(foo) const
  56 ///         {
  57 ///             return foo();
  58 ///         }
  59 ///     };
  60 ///
  61 ///     typedef match_adaptor<int_class, foo_class> fun;
  62 ///
  63 ///     static_assert(std::is_same<int, decltype(fun()(1))>::value, "Failed match");
  64 ///     static_assert(std::is_same<foo, decltype(fun()(foo()))>::value, "Failed match");
  65 ///
  66 ///     int main() {}
  67 ///
  68 /// References
  69 /// ----------
  70 ///
  71 /// * [POO51](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0051r2.pdf) - Proposal for C++
  72 ///   Proposal for C++ generic overload function
  73 ///
  74
  75 #include <boost/hof/reveal.hpp>
  76 #include <boost/hof/detail/callable_base.hpp>
  77 #include <boost/hof/detail/delegate.hpp>
  78 #include <boost/hof/detail/move.hpp>
  79 #include <boost/hof/detail/make.hpp>
  80 #include <boost/hof/detail/static_const_var.hpp>
  81
  82 namespace boost { namespace hof {
  83
  84 template<class...Fs> struct match_adaptor;
  85
  86 template<class F, class...Fs>
  87 struct match_adaptor<F, Fs...> : detail::callable_base<F>, match_adaptor<Fs...>
  88 {
  89     typedef match_adaptor<Fs...> base;
  90     typedef match_adaptor fit_rewritable_tag;
  91
  92     struct failure
  93     : failure_for<detail::callable_base<F>, Fs...>
  94     {};
  95
  96     BOOST_HOF_INHERIT_DEFAULT(match_adaptor, detail::callable_base<F>, base);
  97
  98     template<class X, class... Xs, BOOST_HOF_ENABLE_IF_CONVERTIBLE(X, detail::callable_base<F>), BOOST_HOF_ENABLE_IF_CONSTRUCTIBLE(base, Xs...)>
  99     constexpr match_adaptor(X&& f1, Xs&& ... fs)
 100     : detail::callable_base<F>(BOOST_HOF_FORWARD(X)(f1)), base(BOOST_HOF_FORWARD(Xs)(fs)...)
 101     {}
 102
 103     using F::operator();
 104     using base::operator();
 105 };
 106
 107 template<class F>
 108 struct match_adaptor<F> : detail::callable_base<F>
 109 {
 110     typedef detail::callable_base<F> base;
 111     typedef match_adaptor fit_rewritable_tag;
 112     using F::operator();
 113
 114     BOOST_HOF_INHERIT_CONSTRUCTOR(match_adaptor, detail::callable_base<F>);
 115 };
 116
 117 BOOST_HOF_DECLARE_STATIC_VAR(match, detail::make<match_adaptor>);
 118
 119 }} // namespace boost::hof
 120
 121 #endif