SUBST ===== syntax: (subst <new> <old> <tree> [:test <test>]) ;Common Lisp (tree-substitute <new> <old> <tree> [:test <test>]) ;Babylon Lisp This function exchanges the old elements of the list <tree> against new ones. It does not only work on the list <tree>, but it works too on all lists, which are included in <tree>. example: >(subst 12 1 '((21 1) 3 1)) ((21 12) 3 12)