条款20：为指针的关联容器指定比较类型——effective STL

#include <iostream>#include <iterator>#include <ctime>#include <set>#include <iterator>#include <string>using namespace std;struct StringPtrLess:public binary_function<string*, string*, bool> //使用这个基类的理由参见条款40{bool operator()(const string *ps1, const string *ps2) const{return *ps1 < *ps2;}};int main(){set<string*, StringPtrLess> ssp; ssp.insert(new string("Anteater"));ssp.insert(new string("Wombat"));ssp.insert(new string("Lemur"));ssp.insert(new string("Penguin"));for(set<string*, StringPtrLess>::const_iterator i = ssp.begin(); i != ssp.end(); ++i) cout<<**i<<endl; //编译通不过(类型不匹配)ostream_iterator<string>中参数为string，set为string*//copy(ssp.begin(), ssp.end(), ostream_iterator<string>(cout, "/n")); }