for_each 源码剖析

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一：用法解析

函数原型：

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

功能：

对[ first , last )范围内的元素执行Function操作。

例子：

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

运行如下：
myvector contains: 10 20 30
myvector contains: 10 20 30

二：源码剖析

// TEMPLATE FUNCTION for_eachtemplate<class _InIt,class _Fn1> inlinevoid _For_each(_InIt _First, _InIt _Last, _Fn1& _Func){// perform function for each elementfor (; _First != _Last; ++_First)_Func(*_First);}template<class _InIt,class _Fn1> inline_Fn1 for_each(_InIt _First, _InIt _Last, _Fn1 _Func){// perform function for each element_DEBUG_RANGE_PTR(_First, _Last, _Func);_For_each(_Unchecked(_First), _Unchecked(_Last), _Func);return (_STD move(_Func));}

源码摘抄自Visual Studio 2015安装目录algorithm文件中。

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