std::bind1st, std::bind2nd

C++

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Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Utilities library

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Library feature-test macros
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
integer_sequence (C++14)
Relational operators (deprecated)
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
Elementary string conversions
to_chars (C++17)
from_chars (C++17)
chars_format (C++17)
Type operations
declval (C++11)
as_const (C++17)

Function objects

Function wrappers function (C++11) mem_fn (C++11) bad_function_call (C++11)	Bind bind (C++11) is_bind_expression (C++11) is_placeholder (C++11) _1, _2, _3, ... (C++11)
Function invocation invoke (C++17) Identity function object identity (C++20)	Reference wrappers reference_wrapper (C++11) refcref (C++11)(C++11)
Operator wrappers
plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor bit_not (C++14)
Negators
not_fn (C++17)
Searchers
default_searcher (C++17)
boyer_moore_searcher (C++17)
boyer_moore_horspool_searcher (C++17)
Old binders and adaptors
unary_function (until C++17) binary_function (until C++17) ptr_fun (until C++17) pointer_to_unary_function (until C++17) pointer_to_binary_function (until C++17) mem_fun (until C++17) mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (until C++17)(until C++17)(until C++17)(until C++17) not1 (until C++20) not2 (until C++20)	binder1stbinder2nd (until C++17)(until C++17) bind1stbind2nd (until C++17)(until C++17) mem_fun_ref (until C++17) mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (until C++17)(until C++17)(until C++17)(until C++17) unary_negate (until C++20) binary_negate (until C++20)

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

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)).

Parameters

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

Return value

A function object wrapping f and x.

Exceptions

(none)

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

See also

binder1stbinder2nd (deprecated in C++11)(removed in C++17)

function object holding a binary function and one of its arguments (class template)