std::is_bind_expression (3) - Linux Manuals

std::is_bind_expression: std::is_bind_expression

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 the type produced by a call to std::bind, this template is derived from std::true_type. For any other type, this template is derived from std::false_type.
This template may be specialized for a user-defined type T to implement UnaryTypeTrait with BaseCharacteristic 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.

Helper variable template

template< class T > (since C++17)
inline constexpr bool is_bind_expression_v = is_bind_expression<T>::value;

Inherited from std::integral_constant

Member constants

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

Member functions

              converts the object to bool, returns value
operator bool (public member function)

operator() returns value
              (public member function)
(C++14)

Member types

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

Example

// Run this code

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

  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