大家都體會過sequential container搭配copy() algorithm，只要一行程式就可以將所有值輸出到cout，map這種associative container就無法用這一招，是否有其它方式解決呢?
map這種associative container因為是雙值，若用copy()到cout，會讓cout傻眼，不知道要抓拿一個值，當然用for loop一定可以，但基於使用STL的最高境界：不用for/while loop，此範例我們使用了for_each() algorithm。
1
/*
2
(C) OOMusou 2006 http://oomusou.cnblogs.com
3
4Filename : MapWithfor_each.cpp
5Compiler : Visual C++ 8.0 / ISO C++
6Description : Demo how to use for_each() algorithm to print map.
7Release : 12/14/2006 1.0
8
*/
9
#include <iostream>
10#include <map>
11#include <algorithm>
12#include <string>
13
14using namespace std;
15
16void print(pair<int,string>);
17
18int main() {
19 map<int, string> authors;
20 authors[1] = "Stanley B. Lippman";
21 authors[2] = "Scott Meyers";
22 authors[3] = "Andrei Alexandrescu";
23
24 for_each(authors.begin(), authors.end(), print);
25
26 return 0;
27}
28
29void print(pair<int, string> p) {
30 cout << p.second << endl;
31}
/* 
2
(C) OOMusou 2006 http://oomusou.cnblogs.com3
4
Filename : MapWithfor_each.cpp5
Compiler : Visual C++ 8.0 / ISO C++6
Description : Demo how to use for_each() algorithm to print map.7
Release : 12/14/2006 1.08
*/9
#include <iostream>10
#include <map>11
#include <algorithm>12
#include <string>13
14
using namespace std;15
16
void print(pair<int,string>);17
18
int main() {
19
map<int, string> authors;20
authors[1] = "Stanley B. Lippman";21
authors[2] = "Scott Meyers";22
authors[3] = "Andrei Alexandrescu";23
24
for_each(authors.begin(), authors.end(), print);25
26
return 0;27
}28
29
void print(pair<int, string> p) {30
cout << p.second << endl;31
}
執行結果
1Stanley B. Lippman
2Scott Meyers
3Andrei Alexandrescu
4請按任意鍵繼續 . . .
Stanley B. Lippman2
Scott Meyers3
Andrei Alexandrescu4
請按任意鍵繼續 . . .
使用for_each()的感動雖然不如copy()那樣震撼，但最少程式乾淨了許多。