(union (lambda (x y) (cond ((null x) y) ((member (car x) y) (union (cdr x) y)) (t (cons (car x) (union (cdr x) y))))))
maplist[x;fn]=[null[x]->NIL; t->cons[fn[x];maplist[cdr[x];fn]]]
append[x;y] = [null[x] -> y; T -> cons[car[x]; append[cdr[x];y]]]