(原創) 如何使用for_each() algorithm? (C/C++) (STL)
很怀念VB和C#的foreach语法吗?对于C++只能用for语法造成程序冗长觉得很烦吗?foreach的确对于container而言非常好用且精简，C++/CLI已经增加上了for each语法了，事实上,C++也可使用foreach喔，STL提供了for_each() algorithm，可以弥补这个缺憾。
for_each() algorithm会将每个iterator当作const iterator处理，若只用普通的function，直接将function name传入即可，别忘了function name本身也是个pointer，若要用template function，则必须将该template function转成function pointer才可传进for_each algorithm，以下范例demo for_each() algorithm的用法。
1
/*
2
(C) OOMusou 2006 http://oomusou.cnblogs.com
3
4Filename : GenericAlgo_for_each.cpp
5Compiler : Visual C++ 8.0
6Description : Demo how to use for_each algorithm.
7 Applies a specified function object to each element
8 in a forward order within a range and returns the
9 function object.
10Release : 11/19/2006
11
*/
12
13#include <iostream>
14#include <vector>
15#include <algorithm>
16
17template <class T>
18void coutIterator1(T &);
19
20void coutIterator2(int &);
21
22int main() {
23 std::vector<int> ivec(3,1);
24
25 void (*pf) (int &) = coutIterator1;
26 for_each(ivec.begin(), ivec.end(), pf);
27
28 std::cout << std::endl;
29
30 for_each(ivec.begin(), ivec.end(), coutIterator2);
31
32 return 0;
33}
34
35template <class T>
36void coutIterator1(T &iter) {
37 std::cout << iter << std::endl;
38}
39
40void coutIterator2(int &i) {
41 std::cout << i << std::endl;
42}
/* 
2
(C) OOMusou 2006 http://oomusou.cnblogs.com3
4
Filename : GenericAlgo_for_each.cpp5
Compiler : Visual C++ 8.06
Description : Demo how to use for_each algorithm.7
Applies a specified function object to each element 8
in a forward order within a range and returns the 9
function object.10
Release : 11/19/200611
*/12
13
#include <iostream>14
#include <vector>15
#include <algorithm>16
17
template <class T>18
void coutIterator1(T &);19
20
void coutIterator2(int &);21
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int main() {
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std::vector<int> ivec(3,1);24
25
void (*pf) (int &) = coutIterator1;26
for_each(ivec.begin(), ivec.end(), pf);27
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std::cout << std::endl;29
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for_each(ivec.begin(), ivec.end(), coutIterator2);31
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return 0;33
}34
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template <class T>36
void coutIterator1(T &iter) {37
std::cout << iter << std::endl;38
}39
40
void coutIterator2(int &i) {41
std::cout << i << std::endl;42
}for_each() algorithm不能修改iterator，若要修改iterator，需用transform() algorithm。
See Also
(原創) 如何正確的使用迴圈(使用for_each)? (C/C++) (STL) (template)
Reference
C++ Primer 3rd中文版 P.1145
