Thread: STL's vector V.S. STL's set??

Code:

	int tmp[]={3,2,1,3,2,4,5,4,2};
	vector<int> vc(tmp,tmp+9);
	set<int> st(vc.begin(), vc.end());

	vector<int>::iterator vit=vc.begin();
	for(;vit<vc.end();it++) cout<<*it<<' '; // OK

	set<int>::iterator sit=st.begin();
	for(;sit<st.end();it++) cout<<*it<<' '; // Error
        for(;sit!=st.end();it++) cout<<*it<<' '; // OK

Why '<' is forbidden for SET's iterator?