C++ STL transform_reduce 用法

一：功能

        计算两个向量的内积，它是 std::inner_product 的泛化版本，支持lambda表达式自定义运算。

二：用法

#include <iostream>
#include <vector>
#include <numeric>
#include <execution>
 
int main() {
    std::vector<int> data{1, 2, 3, 4, 5};
    //lambda 自定义运算
    auto sum_of_squares = std::transform_reduce(data.begin(), data.end(),
        0, std::plus<>{}, [](int v) { return v*v; });
    std::cout << "sum_of_squares == " << sum_of_squares << "\n";
    //sum_of_squares = 55
 
    std::vector<int> coef{1, -1, 1, -1, 1};
    auto result = std::transform_reduce(data.begin(), data.end(), 
        coef.begin(), 0);
    std::cout << "result == " << result << "\n";
    //result == 1*1 + 2*(-1) + 3*1 + 4*(-1) + 5*1 == 3
}