Function toLowerInPlace

unittests/catch.hpp:9591–9593

        return static_cast<char>( std::tolower( c ) );
    }
    void toLowerInPlace( std::string& s ) {
        std::transform( s.begin(), s.end(), s.begin(), toLowerCh );
    }
    std::string toLower( std::string const& s ) {
        std::string lc = s;
        toLowerInPlace( lc );