Case insensitive std::set of strings

Question

How do you have a case insensitive insertion Or search of a string in std::set?

For example-

std::set<std::string> s; s.insert("Hello"); s.insert("HELLO"); //not allowed, string already exists. 

Answer 1

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.

Answer 2

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