cpp/regex/sub match/compare

@1@ Compares two directly by comparing their underlying character sequences. Equivalent to.

@2@ Compares a with a std. Equivalent to.

@3@ Compares a with a null-terminated sequence of the underlying character type pointed to by. Equivalent to.

This function is infrequently used directly by application code. Instead, one of the non-member comparison operators is used.

Return value
A value less than zero if this is less than the other character sequence, zero if the both underlying character sequences are equal, greater than zero if this  is greater than the other character sequence.