STL algorithm算法for_each（21）

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

function template

<algorithm>

std::for_each

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

Apply function to range

Applies functionfnto 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 iteratorsto the initial and final positions in a sequence. The range used is[first,last), which contains all the elements betweenfirstandlast, including the element pointed byfirstbut not the element pointed bylast.
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 amove constructiblefunction 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

• C++98
• C++11

Returnsfn, as if callingstd::move(fn).

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; }

Edit & Run

Output:

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

Complexity

Linear in thedistancebetweenfirstandlast: Appliesfnto each element.

Data races

The objects in the range[first,last)are accessed (each object is accessed exactly once).
These objects may be modified ifInputIteratoris amutable iteratortype andfnis not a constant function.

Exceptions

Throws iffnthrows or if any of the operations on iterators throws.
Note that invalid arguments causeundefined 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:[e-mail]

2014-9-13

于GDUT

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