#include <algorithm>
#include <vector>
#include <iostream>

using namespace std;

static int sum = 0;
void add_f(int i )
{
    sum += i * i;

}
void test_using_for_each()
{
    int arr[] = {1,2,3,4};
    vector<int> a (arr,arr + sizeof(arr)/sizeof(arr[0]));

    for_each( a.begin(),a.end(),add_f);
    cout << "sum of the square of the element is  " << sum << endl;
}

在Ruby中,我们可以这样做：

sum = 0
[1,4].each { |i| sum += i*i}   #local variable can be used in the callback function
puts sum    #=> 30

你可以在实践编程中通常使用for_each(不只是打印每个元素)吗？是否可以使用for_each模拟“map”并将其注入到Ruby(或Haskell中的map / fold)中.

#map in ruby 
>> [1,4].map  {|i| i*i} 
=> [1,4,9,16]

#inject in ruby 
[1,16].inject(0)  {|aac,i| aac +=i}  #=> 30

编辑：谢谢大家我从你的答复中学到了很多东西.我们有很多方法在C中做同样的事情,这使得它有点难学.但这很有趣:)

解决方法

#include <vector>
#include <numeric>

// functor for getting sum of prevIoUs result and square of current element
template<typename T>
struct square
{
    T operator()(const T& Left,const T& Right) const
    {   
        return (Left + Right*Right);
    }
};

void main()
{
    std::vector <int> v1;
    v1.push_back(1);
    v1.push_back(2);
    v1.push_back(3);
    v1.push_back(4);

    int x = std::accumulate( v1.begin(),v1.end(),square<int>() );
    // 0 stands here for initial value to which each element is in turn combined with
    // for our case must be 0.
}

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