Can't compile std::map sorting, why?

Question

This is my code:

map<string, int> errs;
struct Compare {
    bool operator() (map<string, int>::const_iterator l, 
        map<string, int>::const_iterator r) { 
        return ((*l).second < (*r).second); 
    }
} comp;
sort(errs.begin(), errs.end(), comp);

Can't compile. This is what I'm getting:

no matching function for call to ‘sort(..’

Why so? Can anyone help? Thanks!

Answer 1

You can't sort a map. It has its own sort order, defined at construction time either as the default (use <) or a passed in comparator.