std::match_results<BidirIt,Alloc>::begin, std::match_results<BidirIt,Alloc>::cbegin
Min standard notice:
Returns an iterator to the beginning of the list of sub-matches. If match was successful, the iterator will point to the entire matched expression.
# Declarations
iterator begin() noexcept;
(since C++11)
const_iterator begin() const noexcept;
(since C++11)
const_iterator cbegin() const noexcept;
(since C++11)
# Return value
Iterator to the first sub-match.