std::is_bind_expression

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

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.

Inherited from std::integral_constant

Member constants

value

[static]

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

Member functions

operator bool

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

Member types

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

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.

[edit] 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::operator(), _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

[edit] See also

bind

(C++11)

binds one or more arguments to a function object
(function template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
Relational operators
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Pairs and tuples
pair
tuple (C++11)
piecewise_construct_t (C++11)
piecewise_construct (C++11)
Swap, forward and move
swap
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
declval (C++11)