std::multiplies<void>

 

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定義於標頭檔案 <functional>
template<> class multiplies<void>;		(C++14 起)

std::multiplies<void> 是 std::multiplies 的一個特化，其引數和返回型別被推導。

成員型別

型別	定義
is_transparent	未指定

成員函式

operator()

返回兩個實參的乘積 (公開成員函式)

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));

返回 lhs 和 rhs 的乘積。

引數

lhs, rhs

-

要相乘的值

返回值

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

示例

執行此程式碼

#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';
}

輸出

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