mapcon

(mapcon function list)

Like maplist, function is applied to successive tails of list, but the resulting lists are concatenated into one (the tail-walking counterpart of mapcan). The pieces are joined with append. Single-list form only.

The argument must be a list (nil, the empty list, is accepted); passing a non-list such as a string signals an error rather than silently returning nil. Use map to map over a string or vector.