SketchyLISP Reference |
Copyright (C) 2007 Nils M Holm |
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Conformance: SketchyLISP Extension
Purpose: Check whether an expression is the head of another.
Arguments:
X - potential head
Y - expression
Implementation:
(define (head? x y) (cond ((null? y) (null? x)) ((null? x) #t) ((equal? (car x) (car y)) (head? (cdr x) (cdr y))) (else #f)))
Example:
(head? '(a b c) '(a b c d e f)) => #t
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