mapcon

(mapcon function list &rest more-lists)

Like maplist, function is applied to successive tails of the given lists, but the resulting lists are concatenated into one (the tail-walking counterpart of mapcan). The pieces are joined with append; a piece that is not a list signals a type-error. When several lists are supplied, the function is called with one tail from each list in parallel, and iteration stops at the end of the shortest list.

Each argument must be a list (nil, the empty list, is accepted); passing a non-list such as a string, or a dotted list the walk reaches the end of, signals a type-error rather than silently returning nil. Use map to map over a string or vector.