Method iterator

unittests/catch.hpp:5467–5475

            size_t m_activeIterators;

            iterator( Columns const& columns, EndTag )
            :   m_columns( columns.m_columns ),
                m_activeIterators( 0 )
            {
                m_iterators.reserve( m_columns.size() );

                for( auto const& col : m_columns )
                    m_iterators.push_back( col.end() );
            }

        public:
            explicit iterator( Columns const& columns )