std::binder1st, std::binder2nd
template< class Fn > class binder1st : public std::unary_function<typename Fn::second_argument_type, |
(1) | (deprecated in C++11) (removed in C++17) |
template< class Fn > class binder2nd : public unary_function<typename Fn::first_argument_type, |
(2) | (deprecated in C++11) (removed in C++17) |
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.
value
given at the construction of the object.value
given at the construction of the object.Example
#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:
0 deg = 0 rad (using binder) 0 rad (using lambda) 30 deg = 0.523599 rad (using binder) 0.523599 rad (using lambda) 45 deg = 0.785398 rad (using binder) 0.785398 rad (using lambda) 60 deg = 1.0472 rad (using binder) 1.0472 rad (using lambda) 90 deg = 1.5708 rad (using binder) 1.5708 rad (using lambda) 180 deg = 3.14159 rad (using binder) 3.14159 rad (using lambda)
See also
(deprecated in C++11)(removed in C++17) |
binds one argument to a binary function (function template) |