commit 9ecbaa7ab7663d0a2b6fbb35f9de650b2727e65b parent dde8a9369d5f76e2dfeb0828c2e732993c21ccf6 Author: Ed van Bruggen <edvb@uw.edu> Date: Sat, 28 Dec 2019 21:41:34 -0800 Add error message to nth for out of bounds Diffstat:
| tibs/lib.tsp | | | 6 | ++++-- |
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/tibs/lib.tsp b/tibs/lib.tsp @@ -121,11 +121,13 @@ (last (cdr lst)) (car lst))) +; TODO make nth generic for list str vec, made up of list-ref vec-ref str-ref (define (nth lst i) - (when (pair? lst) + (if (pair? lst) (if (<= i 0) (car lst) - (nth (cdr lst) (- i 1))))) + (nth (cdr lst) (- i 1))) + (error 'nth "index of list out bounds"))) (define (count x lst) (cond ((nil? lst) 0)