class interface DS_PAIR[G,H] creation make (v: G; w: H) -- Create a new cell containing v and w. ensure first_set: first = v; second_set: second = w feature(s) from DS_CELL -- Access first: G -- Content of cell feature(s) from DS_CELL -- Element change put_first (v: G) -- Insert v in cell. ensure inserted: first = v feature(s) from DS_CELL -- Element change make_first (v: G) -- Insert v in cell. ensure inserted: first = v feature(s) from DS_PAIR -- Access second: H -- Second item of cell feature(s) from DS_PAIR -- Element change put_second (w: H) -- Insert w in cell. ensure inserted: second = w end of DS_PAIR[G,H]