table of contents
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 retroactively to
previously published C++ standards.
DR Applied to Behavior as published Correct behavior
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)
2024.06.10 | http://cppreference.com |