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。
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/**/ /* 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 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";2324 for_each(authors.begin(), authors.end(), print);2526 return 0;27} 28 29 void print(pair < int , string > p) { 30 cout << p.second << endl;31}
執行結果 /**/ /* 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 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";2324 for_each(authors.begin(), authors.end(), print);2526 return 0;27} 28 29 void print(pair < int , string > p) { 30 cout << p.second << endl;31} 1 Stanley B. Lippman 2 Scott Meyers 3 Andrei Alexandrescu 4 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。See Also Stanley B. Lippman 2 Scott Meyers 3 Andrei Alexandrescu 4 請按任意鍵繼續 . . .