Case insensitive std::set of strings

You need to define a custom comparator:

struct InsensitiveCompare { 
    bool operator() (const std::string& a, const std::string& b) const {
        return strcasecmp(a.c_str(), b.c_str()) < 0;
    }
};

std::set<std::string, InsensitiveCompare> s;

You may try stricmp or strcoll if strcasecmp is not available.

std::set offers the possibility of providing your own comparer (as do most std containers). You can then perform any type of comparison you like. Full example is available here