std::bind1st, std::bind2nd - cppreference.com (original) (raw)

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)).

[edit] Parameters

[edit] Return value

A function object wrapping f and x.

[edit] Exceptions

May throw implementation-defined exceptions.

[edit] Example

#include #include #include #include #include #include #include   int main() { std::vector a = {0, 30, 45, 60, 90, 180}; std::vector r(a.size()); const double pi = std::acos(-1); // since C++20 use std:🔢:pi   std::transform(a.begin(), a.end(), r.begin(), std::bind1st(std::multiplies(), pi / 180.0)); // an equivalent lambda is: [pi](double a) { return a * pi / 180.0; });   for (std::size_t n = 0; n < a.size(); ++n) std::cout << std::setw(3) << a[n] << "° = " << std::fixed << r[n] << " rad\n" << std::defaultfloat; }

Output:

0° = 0.000000 rad 30° = 0.523599 rad 45° = 0.785398 rad 60° = 1.047198 rad 90° = 1.570796 rad 180° = 3.141593 rad

[edit] See also