std::match_results<BidirIt,Alloc>::length

difference_type length( size_type n = 0 ) const;

(since C++11)

Returns the length of the specified sub-match.

If n == 0, the length of the entire matched expression is returned.

If n > 0 && n < size(), the length of nth sub-match is returned.

if n >= size(), a length of the unmatched match is returned.

The call is equivalent to (*this)[n].length().

integral number specifying which match to examine

The length of the specified match or sub-match.

operator[]	returns specified sub-match (public member function)
length	returns the length of the match (if any) (public member function of `std::sub_match<BidirIt>`)