/ Published in: Lisp
This one drove me crazy because of the requirement to return -1 if s not in los.
(list-index s los) returns the zero-based index of the first
occurence of s in los, or -1 if there is no occurences of s in los.
(list-index s los) returns the zero-based index of the first
occurence of s in los, or -1 if there is no occurences of s in los.