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Posted By

gleather on 01/14/08


Tagged

scheme list-index eopl


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list-index (Scheme)

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.


Plain TextExpand 
  1. (define list-index
  2.         (lambda (s los)
  3.                 (if (null? los)
  4.                         -1
  5.                         (if (eq? (car los) s)
  6.                                 0
  7.                                 (if (= (list-index s (cdr los)) -1) 
  8.                                         -1
  9.                                         (+ 1 (list-index s (cdr los))))))))

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