/ 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.
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(define list-index (lambda (s los) (if (null? los) -1 (if (eq? (car los) s) 0 (if (= (list-index s (cdr los)) -1) -1 (+ 1 (list-index s (cdr los))))))))