syndicate-lang
/
racket-matrix-2012
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
unify.rkt
View File

@ -10,6 +10,7 @@
wild wild
wild? wild?
non-wild? non-wild?
ground?
variables-in variables-in
unify unify
unify/env unify/env
@ -69,12 +70,24 @@
(define (variables-in x) (define (variables-in x)
(let walk ((x x) (acc (set))) (let walk ((x x) (acc (set)))
(cond (cond
[(variable? x) (set-add acc x)] [(wild? x) (set-add acc x)]
[(pair? x) (walk (car x) (walk (cdr x) acc))] [(pair? x) (walk (car x) (walk (cdr x) acc))]
[(vector? x) (foldl walk acc (vector->list x))] [(vector? x) (foldl walk acc (vector->list x))]
[(non-object-struct? x) (walk (struct->vector x #f) acc)] [(non-object-struct? x) (walk (struct->vector x #f) acc)]
[else 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 ;; Variable Any -> Boolean
(define (occurs? var val) (define (occurs? var val)
(let walk ((x val)) (let walk ((x val))