为包含指针的关联容器指定比较类型

#include <iostream>#include <string>#include <algorithm>#include <iterator>#include <set>using namespace std;class DereferenceLess{public:template<typename T>bool operator()(const T* ptr1,const T* ptr2){return *ptr1<*ptr2;}};class Deference{public:template<typename T>const T& operator()(const T* ptr){return *ptr;}};int main(){set<string*,DereferenceLess> ssp;ssp.insert(new string("Anteater"));ssp.insert(new string("Wombat"));ssp.insert(new string("Lemur"));ssp.insert(new string("Penguin"));transform(ssp.begin(),ssp.end(),ostream_iterator<string>(cout,"\n"),Deference());return 0;}