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racket-matrix-2012
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Add ground? and fix variables-in

This commit is contained in:
Tony Garnock-Jones 2012-05-11 14:57:50 -04:00
parent 634e795a6c
commit f1f7cc0d8c
1 changed files with 14 additions and 1 deletions
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15
unify.rkt
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@ -10,6 +10,7 @@
wild
wild?
non-wild?
ground?
variables-in
unify
unify/env
@ -69,12 +70,24 @@
(define (variables-in x)
(let walk ((x x) (acc (set)))
(cond
[(variable? x) (set-add acc x)]
[(wild? x) (set-add acc x)]
[(pair? x) (walk (car x) (walk (cdr x) acc))]
[(vector? x) (foldl walk acc (vector->list x))]
[(non-object-struct? x) (walk (struct->vector x #f) acc)]
[else acc])))
;; Any -> Boolean
;; True iff the term is completely ground, that is has no variables or
;; canonical-variables in it.
(define (ground? x)
(let walk ((x x))
(cond
[(wild? x) #f]
[(pair? x) (and (walk (car x)) (walk (cdr x)))]
[(vector? x) (andmap walk (vector->list x))]
[(non-object-struct? x) (walk (struct->vector x #f))]
[else #t])))
;; Variable Any -> Boolean
(define (occurs? var val)
(let walk ((x val))