<boost/url/grammar/ci_string.hpp>
using ci_equal = /* implementation-defined */;
The function object returns true
when two strings are equal, ignoring case. This is a suitable equality predicate for unordered containers. The function is defined only for strings containing low-ASCII characters.
boost::unordered_map< std::string, std::string, ci_hash, ci_equal > m1;
std::unordered_map < std::string, std::string, ci_hash, ci_equal > m2; // (since C++20)