std::bind1st, std::bind2nd
From cppreference.com
< cpp | utility | functional
| Defined in header <functional>
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| 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
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[edit] Return value
A function object wrapping f and x.
[edit] Exceptions
(none)
[edit] Example
Run this code
#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) |