The match_results::operator is a built function in C++ which used to get the i-th match in the match_result object. It gives the reference to the match at the position given inside the operator.
smatch_name[N] Note: smatch_name is an object of match_results class.
Parameters: It accepts a single parameter N which specifies the Match number. It is lower than match_results::size. The match number 0 represents the entire matched expression. Subsequent match numbers identify the sub-expressions if any. The passed integral is an unsigned integral type.
Return value: It returns the direct reference to the match at the N-th match.
Note: First element always contains the whole regex match while the others conatain the particular Capturing Group.
Below programs illustrates the above function.
Matches are: match 0 is Geeksforgeeks match 1 is Geeks match 2 is forgeeks
max-length sub match is forgeeks with a length of 8