std:: multiplies<void>

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C++
Utilities library
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Relational operators (deprecated in C++20)
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Old binders and adaptors
( until C++17* )
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( until C++17* )
( until C++17* ) ( until C++17* ) ( until C++17* ) ( until C++17* )
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( until C++20* )
Defined in header <functional>
template <>
class multiplies < void > ;
(since C++14)

std:: multiplies < void > is a specialization of std::multiplies with parameter and return type deduced.

Member types

Type Definition
is_transparent unspecified

Member functions

operator()
returns the product of two arguments
(public member function)

std::multiplies<void>:: operator()

template < class T, class U >

constexpr auto operator ( ) ( T && lhs, U && rhs ) const

- > decltype ( std:: forward < T > ( lhs ) * std:: forward < U > ( rhs ) ) ;

Returns the product of lhs and rhs .

Parameters

lhs, rhs - values to multiply

Return value

std:: forward < T > ( lhs ) * std:: forward < U > ( rhs ) .

Example

Run this code 
#include <complex>
#include <functional>
#include <iostream>
 
int main()
{
    auto complex_multiplies = std::multiplies<void>{}; // “void” can be omitted
    constexpr std::complex z1{1.0, 2.0}, z2{3.0, 4.0};
 
    std::cout << std::showpos
              << complex_multiplies(z1, z2) << ' ' << z1 * z2 << '\n'
              << complex_multiplies(z1, 5.) << ' ' << z1 * 5. << '\n'
              << complex_multiplies(5., z1) << ' ' << 5. * z1 << '\n';
}

Output: 

(-5,+10) (-5,+10)
(+5,+10) (+5,+10)
(+5,+10) (+5,+10)
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