home | help 
std::is_bind_expression(3)     C++ Standard Libary    std::is_bind_expression(3)

NAME
     std::is_bind_expression - std::is_bind_expression

Synopsis
	Defined in header <functional>
	template< class T >		(since C++11)
	struct is_bind_expression;

	If  T is a type produced by a call to std::bind (but not std::bind_front
     or
	std::bind_back), this template is derived from std::true_type.	For  any
     other type
	(unless    user-specialized),	 this	 template    is   derived   from
     std::false_type.

	A program may specialize this template for a program-defined type  T  to
     implement
	UnaryTypeTrait	with  base  characteristic of std::true_type to indicate
     that T should
	be treated by std::bind as if it were the type of a bind  subexpression:
     when a
	bind-generated function object is invoked, a bound argument of this type
     will be
	invoked as a function object and will be given all the unbound arguments
     passed to
	the bind-generated object.

Member constants
	value	  true	if  T is a function object generated by std::bind, false
     otherwise
	[static] (public static member constant)

Member functions
	operator bool converts the object to bool, returns value
		      (public member function)
	operator()    returns value
	(C++14)       (public member function)

Member types
	Type	   Definition
	value_type bool
	type	   std::integral_constant<bool, value>

Example
     // Run this code

      #include <functional>
      #include <iostream>
      #include <type_traits>

      struct MyBind
      {
	  typedef int result_type;
	  int operator()(int a, int b) const { return a + b; }
      };

      namespace std
      {
	  template<>
	  struct is_bind_expression<MyBind> : public true_type {};
      }

      int f(int n1, int n2)
      {
	  return n1 + n2;
      }

      int main()
      {
	  // as if bind(f, bind(MyBind(), _1, _2), 2)
	  auto b = std::bind(f, MyBind(), 2);

	  std::cout << "Adding 2 to the sum of 10 and 11 gives " << b(10, 11) <<
     '\n';
      }

Output:
      Adding 2 to the sum of 10 and 11 gives 23

	Defect reports

	The following behavior-changing defect	reports  were  applied	retroac-
     tively to
	previously published C++ standards.

	   DR	  Applied  to	      Behavior as published	     Correct be-
     havior
	LWG 2010 C++11	    program-defined specializations could can be derived
     from
			    only be derived from std::false_type  std::true_type

See also
	bind	binds one or more arguments to a function object
	(C++11) (function template)

http://cppreference.com 	   2024.06.10	      std::is_bind_expression(3)
home | help