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  1. #include <type_traits>
  2. #include <iostream>
  3. #include <string>
  4. #include <typeinfo>
  5. #include <utility>
  6. #include <tuple>
  7.  
  8.  
  9. struct context{};
  10.  
  11. template<class T> auto pass(const context& c) noexcept
  12. {
  13.     using arg = ::std::remove_cv_t<
  14.         ::std::remove_reference_t<T> 
  15.     >;
  16.  
  17.     std::cout << "type = " << typeid(T).name() << std::endl;
  18.     return arg{};
  19. }
  20.  
  21. void some_function(int v1, bool v2, const std::string& v3) noexcept
  22. {
  23.     std::cout << "call(" 
  24.         << v1 << ", " 
  25.         << std::boolalpha << v2 <<" , \"" 
  26.         << v3 <<"\" );\n";
  27. }
  28.  
  29.  
  30. template<typename F, typename ArgsTuple, std::size_t ...Indices>
  31. auto apply(F && f, ArgsTuple && args, std::index_sequence<Indices...>) {
  32.    return std::forward<F>(f)(std::get<Indices>(std::forward<ArgsTuple>(args))...);
  33. }
  34.  
  35.  
  36. template<class... Args> void expand(const Args&...) 
  37. {
  38.     using tuple_type = std::tuple<std::remove_cv_t<decltype(pass<Args>(std::declval<context>()))>...>;
  39.  
  40.     context ctx;
  41.     tuple_type args { pass<Args>(ctx)... };
  42.  
  43.     apply(some_function,
  44.          std::move(args),
  45.          std::make_index_sequence<sizeof...(Args)> {});
  46. }
  47.  
  48. int main()
  49. {
  50.     expand(42, true, std::string { "answer" });
  51. }
  52.  
Success #stdin #stdout 0s 4484KB
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stdin
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Standard input is empty
stdout
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type = i
type = b
type = NSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
call(0, false , "" );
https://ideone.com/4W8bX6
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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