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std::bind1st, std::bind2nd

From cppreference.com
< cpp‎ | utility‎ | functional
 
 
 
Function objects
Function wrappers
(C++11)
(C++11)
(C++17)
Bind
(C++11)
Reference wrappers
(C++11)(C++11)
Default ordering


Operator wrappers
Negators
(deprecated)
(deprecated)

(deprecated)
(deprecated)
Searchers
Old binders and adaptors
(until C++17)
(until C++17)
(until C++17)
(until C++17)
(until C++17)(until C++17)(until C++17)(until C++17)
(until C++17)(until C++17)
bind1stbind2nd
(until C++17)(until C++17)

(until C++17)
(until C++17)(until C++17)(until C++17)(until C++17)
 
Defined in header <functional>
template< class F, class T >
std::binder1st<F> bind1st( const F& f, const T& x );
(1) (until C++17)
(deprecated since C++11)
template< class F, class T >
std::binder2nd<F> bind2nd( const F& f, const T& x );
(2) (until C++17)
(deprecated since C++11)

Binds a given argument x to a first or second parameter of the given binary function object f. That is, stores x within the resulting wrapper, which, if called, passes x as the first or the second parameter of f.

1) Binds the first argument of f to x. Effectively calls std::binder1st<F>(f, typename F::first_argument_type(x)).

2) Binds the second argument of f to x. Effectively calls std::binder2nd<F>(f, typename F::second_argument_type(x)).

Contents

[edit] Parameters

f - pointer to a function to bind an argument to
x - argument to bind to f

[edit] Return value

A function object wrapping f and x.

[edit] Exceptions

(none)

[edit] Example

#include <iostream>
#include <algorithm>
#include <functional>
#include <cmath>
#include <vector>
 
int main()
{
    std::vector<double> a= {0, 30, 45, 60, 90, 180};
    std::vector<double> r(a.size());
    double pi = std::acos(-1);
 
    std::transform(a.begin(), a.end(), r.begin(),
        std::bind1st(std::multiplies<double>(), pi / 180.));
// equivalent lambda: [pi](double a){ return a*pi/180.; });
 
    for(size_t n = 0; n < a.size(); ++n)
        std::cout << a[n] << " deg = " << r[n] << " rad\n";
}

Output:

0 deg = 0 rad
30 deg = 0.523599 rad
45 deg = 0.785398 rad
60 deg = 1.0472 rad
90 deg = 1.5708 rad
180 deg = 3.14159 rad

[edit] See also

(until C++17)(until C++17)
function object holding a binary function and one of its arguments
(class template) [edit]