SketchyLISP Reference |
Copyright (C) 2007 Nils M Holm |
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Conformance: SketchyLISP Core
Purpose:
Find the predecessor of a decimal digit.
(pred 0d) => ().
Arguments:
X - symbol representing a digit
Implementation:
(define (pred x) (cond ((eq? x 0d) '()) ((eq? x 1d) 0d) ((eq? x 2d) 1d) ((eq? x 3d) 2d) ((eq? x 4d) 3d) ((eq? x 5d) 4d) ((eq? x 6d) 5d) ((eq? x 7d) 6d) ((eq? x 8d) 7d) ((eq? x 9d) 8d) (else (bottom 'digit 'expected))))
Example:
(pred 5d) => 4d
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