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trie-step-wild

This commit is contained in:
Sam Caldwell 2017-07-31 11:39:44 -04:00
parent 852e93328f
commit 5f621b098e
1 changed files with 24 additions and 0 deletions
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24
racket/syndicate/trie.rkt
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@ -53,6 +53,7 @@
;; trie-prune-branch
trie-step
trie-step*
trie-step-wild
projection->pattern
instantiate-projection
@ -678,6 +679,29 @@
(define (trie-step* t keys)
(foldl (lambda (key t) (trie-step t key)) t keys))
;; Trie -> Trie
(define (trie-step-wild t)
;; Trie Natural -> Trie
(define (walk t n)
(match* (t n)
[(_ 0) t]
[((branch os w rs) _)
(define n-1 (sub1 n))
(define w-k (walk w n-1))
(define o-ks
(for/fold ([acc w-k])
([entry (treap-to-alist os)])
(match-define (cons (open-parenthesis arity _) k) entry)
(trie-union acc (walk (walk k arity) n-1))))
(for/fold ([acc o-ks])
([entry (treap-to-alist rs)])
(match-define (cons _ k) entry)
(trie-union acc (walk k n-1)))]
[(_ _)
trie-empty]))
(walk t 1))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Projection