原文地址：http://www.cplusplus.com/reference/algorithm/for_each/

std::for_each

template <class InputIterator, class Function>
   Function for_each (InputIterator first, InputIterator last, Function fn);

Applies function fn to each of the elements in the range [first,last).
对范围内每个元素都调用函数fn.例子：

#include <iostream>
#include <algorithm>
#include <vector>
#include <array>
using namespace std;

void foreach(){
    vector<int> vi{1,5,7,8,9,9,8,5,9};
    cout<<"vi=";
    auto it=for_each(vi.begin(),vi.end(),[](int i){cout<<i<<" ";});
    cout<<endl;
}

运行结果：

The behavior of this template function is equivalent to:

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template<class InputIterator, class Function>
  Function for_each(InputIterator first, InputIterator last, Function fn)
{
  while (first!=last) {
    fn (*first);
    ++first;
  }
  return fn;      // or, since C++11: return move(fn);
}

Parameters

first, last

Input iterators to the initial and final positions in a sequence. The range used
is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
元素的范围。

fn

Unary function that accepts an element in the range as argument.
This can either be a function pointer or a move constructible function object.
Its return value, if any, is ignored.
一个接受一个参数的一元函数。
该函数的返回值会被忽略。

Return value

返回的是一个仿函数fn,这个我也不知道怎么用…

Example

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// for_each example
#include <iostream>     // std::cout
#include <algorithm>    // std::for_each
#include <vector>       // std::vector

void myfunction (int i) {  // function:
  std::cout << ' ' << i;
}

struct myclass {           // function object type:
  void operator() (int i) {std::cout << ' ' << i;}
} myobject;

int main () {
  std::vector<int> myvector;
  myvector.push_back(10);
  myvector.push_back(20);
  myvector.push_back(30);

  std::cout << "myvector contains:";
  for_each (myvector.begin(), myvector.end(), myfunction);
  std::cout << '\n';

  // or:
  std::cout << "myvector contains:";
  for_each (myvector.begin(), myvector.end(), myobject);
  std::cout << '\n';

  return 0;
}

Output:

myvector contains: 10 20 30
myvector contains: 10 20 30

Complexity

Linear in the distance between first and last: Applies fn to each element.

Data races

The objects in the range [first,last) are accessed (each object is accessed exactly once).
These objects may be modified if InputIterator is a mutable iterator type and fn is not a constant function.

Exceptions

Throws if fn throws or if any of the operations on iterators throws.
Note that invalid arguments cause undefined behavior.

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//写的错误或者不好的地方请多多指导，可以在下面留言或者点击左上方邮件地址给我发邮件，指出我的错误以及不足，以便我修改，更好的分享给大家，谢谢。

转载请注明出处：http://blog.csdn.net/qq844352155

author:天下无双

Email:coderguang@gmail.com

2014-9-13

于GDUT

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