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  1. #include <utility>
  2. #include <functional>
  3. #include <iostream>
  4.  
  5.     template<class Is, size_t I>
  6.     struct add;
  7.     template<class Is, size_t I>
  8.     using add_t=typename add<Is,I>::type;
  9.  
  10.     template<size_t...Is, size_t I>
  11.     struct add<std::index_sequence<Is...>, I>{
  12.       using type=std::index_sequence<(I+Is)...>;
  13.     };
  14.  
  15.     template<template<class...>class Z, class Is, class...Ts>
  16.     struct partial_apply;
  17.     template<template<class...>class Z, class Is, class...Ts>
  18.     using partial_apply_t=typename partial_apply<Z,Is,Ts...>::type;
  19.  
  20.     template<template<class...>class Z, size_t...Is, class...Ts>
  21.     struct partial_apply<Z,std::index_sequence<Is...>, Ts...> {
  22.       using tup = std::tuple<Ts...>;
  23.       template<size_t I> using e = std::tuple_element_t<I, tup>;
  24.  
  25.       using type=Z< e<Is>... >;
  26.     };
  27.  
  28.     template<template<class...>class Z, class...Ts>
  29.     struct split {
  30.       using left = partial_apply_t<Z, std::make_index_sequence<sizeof...(Ts)/2>, Ts...>;
  31.       using right = partial_apply_t<Z, add_t<
  32.         std::make_index_sequence<(1+sizeof...(Ts))/2>,
  33.         sizeof...(Ts)/2
  34.       >, Ts...>;
  35.     };
  36.     template<template<class...>class Z, class...Ts>
  37.     using right=typename split<Z,Ts...>::right;
  38.     template<template<class...>class Z, class...Ts>
  39.     using left=typename split<Z,Ts...>::left;
  40.  
  41.     template<class...Sigs>
  42.     struct functions_impl;
  43.  
  44.     template<class...Sigs>
  45.     using functions = typename functions_impl<Sigs...>::type;
  46.  
  47.     template<class...Sigs>
  48.     struct functions_impl:
  49.       left<functions, Sigs...>,
  50.       right<functions, Sigs...>
  51.     {
  52.        using type=functions_impl;
  53.        using A = left<functions, Sigs...>;
  54.        using B = right<functions, Sigs...>;
  55.        using A::operator();
  56.        using B::operator();
  57.        template<class F>
  58.        functions_impl(F&& f):
  59.          A(f),
  60.          B(std::forward<F>(f))
  61.        {}
  62.     };
  63.     template<class Sig>
  64.     struct functions_impl<Sig> {
  65.       using type=std::function<Sig>;
  66.     };
  67.  
  68. int main()
  69. {
  70. 	functions<void(int), void(double)> f = [](auto&& x){std::cout << x << '\n';};
  71. 	f(3.14);
  72. 	f(3);
  73. }
Success #stdin #stdout 0s 3460KB
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Standard input is empty
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3.14
3
https://ideone.com/8W1FvT
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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