std :: multiplied在C++中

用于执行乘法的函数对象。在两个T类型的实例上有效地调用运算符* 。

句法 ：

template  struct multiplies : binary_function  
{
    T operator() (const T& x, const T& y) const {return x*y;}
};

Template Parameters :
T - Type of the arguments and return type of the functional call.
    The type shall support the operation (operator*).

Member types :
x : Type of the first argument in member operator()
y : Type of the second argument in member operator()
result_type : Type returned by member operator()

例子 ：

// C++ program to illustrate std::multiplies
// by multiplying the respective elements of 2 arrays
#include  // std::cout
#include  // std::multiplies
#include  // std::transform
  
int main()
{
    // First array
    int first[] = { 1, 2, 3, 4, 5 };
  
    // Second array
    int second[] = { 10, 20, 30, 40, 50 };
  
    // Result array
    int results[5];
  
    // std::transform applies std::multiplies to the whole array
    std::transform(first, first + 5, second, results, std::multiplies());
  
    // Printing the result array
    for (int i = 0; i < 5; i++)
        std::cout << results[i] << " ";
  
    return 0;
}

输出：

10 40 90 160 250 

另一个例子 ：

// C++ program to illustrate std::multiplies
// by multiplying all array elements with a number
#include 
  
int main()
{
    // Array with elements to be multiplying
    int arr[] = { 10, 20, 30 };
  
    // size of array
    int size = sizeof(arr) / sizeof(arr[0]);
  
    // Variable with which array is to be multiplied
    int num = 10;
  
    // Variable to store result
    int result;
  
    // using std::accumulate to perform multiplication on array with num
    // using std::multiplies
    result = std::accumulate(arr, arr + size, num, std::multiplies());
  
    // Printing the result
    std::cout << "The result of 10 * 10 * 20 * 30 is " << result;
  
    return 0;
}

输出：

60000

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