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