Method substring

extras/catch_amalgamated.cpp:7954–7969

        }

        std::string AnsiSkippingString::substring( const_iterator begin,
                                                   const_iterator end ) const {
            // There's one caveat here to an otherwise simple substring: when
            // making a begin iterator we might have skipped ansi sequences at
            // the start. If `begin` here is a begin iterator, skipped over
            // initial ansi sequences, we'll use the true beginning of the
            // string. Lastly: We need to transform any chars we replaced with
            // 0xff back to 'm'
            auto str = std::string( begin == this->begin() ? m_string.begin()
                                                           : begin.m_it,
                                    end.m_it );
            std::transform( str.begin(), str.end(), str.begin(), []( char c ) {
                return c == AnsiSkippingString::sentinel ? 'm' : c;
            } );
            return str;
        }

        void AnsiSkippingString::const_iterator::tryParseAnsiEscapes() {
            // check if we've landed on an ansi sequence, and if so read through