std::binder1st,std::binder2nd (3) Linux Manual Page
std::binder1st,std::binder2nd – std::binder1st,std::binder2nd
Synopsis
template< class Fn >
class binder1st : public std::unary_function<typename Fn::second_argument_type,
typename Fn::result_type> {
protected:
Fn op;
typename Fn::first_argument_type value;
public:
(deprecated in C++ 11)(1)(removed in C++ 17)
binder1st(const Fn &fn,
const typename Fn::first_argument_type &value);
typename Fn::result_type
operator()(const typename Fn::second_argument_type &x) const;typename Fn::result_type
operator()(typename Fn::second_argument_type& x) const;
};
template< class Fn >
class binder2nd : public unary_function<typename Fn::first_argument_type,
typename Fn::result_type> {
protected:
Fn op;
typename Fn::second_argument_type value;
public:
binder2nd(const Fn& fn, (2) (deprecated in C++11)
const typename Fn::second_argument_type& value); (removed in C++17)
typename Fn::result_type
operator()(const typename Fn::first_argument_type &x) const;
typename Fn::result_type
operator()(typename Fn::first_argument_type &x) const;
}
;A function object that binds an argument to a binary function.
The value of the parameter is passed to the object at the construction time and stored within the object. Whenever the function object is invoked though operator(), the stored value is passed as one of the arguments, the other argument is passed as an argument of operator(). The resulting function object is an unary function.
1) Binds the first parameter to the value value given at the construction of the object.
2) Binds the second parameter to the value value given at the construction of the object.
Example
// Run this code
#include <iostream>
#include <functional>
#include <cmath>
#include <vector>
const double pi = std::acos(-1);
int main()
{
// deprecated in C++11, removed in C++17
std::binder1st<std::multiplies<double>> f1 = std::bind1st(
std::multiplies<double>(), pi / 180.);
// C++11 replacement
auto f2 = [](double a) { return a * pi / 180.; };
for (double n : {0, 30, 45, 60, 90, 180})
std::cout << n << " deg = " << f1(n) << " rad (using binder) "
<< f2(n) << " rad (using lambda)\n";
}
Output:
See also
bind1st binds one argument to a binary function
bind2nd (function template)
(deprecated in C++11)(removed in C++17)