/usr/lib/s9fes/tree-equalp.scm is in scheme9 2010.11.13-2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | ; Scheme 9 from Empty Space, Function Library
; By Nils M Holm, 2010
; See the LICENSE file of the S9fES package for terms of use
;
; (tree-equal? procedure pair1 pair2) ==> boolean
;
; Compare the leaves of two trees PAIR1 and PAIR2 using the predicate
; PROCEDURE. TREE-EQUAL? returns #T if the trees have the same structure
; and (procedure x1 x2) holds for their pairwise leaves.
;
; Example: (tree-equal? (lambda (x y) #t)
; '(((a . b) (c . d)) (e . f))
; '(((1 . 2) (3 . 4)) (5 . 6))) ==> #t
;
; (tree-equal? eqv?
; '((1 . 2) (3 . 4))
; '((1 . 2) (3 4))) ==> #f
(define (tree-equal? p t1 t2)
(if (pair? t1)
(and (pair? t2)
(tree-equal? p (car t1) (car t2))
(tree-equal? p (cdr t1) (cdr t2)))
(p t1 t2)))
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