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Add the ability to remove keys from a hash table.

This commit is contained in:
Jesse D. McDonald 2011-04-25 15:48:46 -05:00
parent a2a5532703
commit 99da463f84
2 changed files with 58 additions and 8 deletions
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36
src/hash-table.rls
View File

@ -82,4 +82,40 @@
(hash-table-node-right-child-set! node (hash-table-node-right-child-set! node
(make-hash-table-node hash key val))))])))))) (make-hash-table-node hash key val))))]))))))
(define (hash-table-remove ht key [not-found (lambda () #f)])
(let ([hash ((hash-table-hash-function ht) key)]
[eq-fn (hash-table-eq-function ht)])
(let search ([node (hash-table-root-node ht)]
[replace-node! (lambda (n) (hash-table-root-node-set! ht n))])
(if node
(let ([node-hash (hash-table-node-hash node)])
(cond
[(and (fix= hash node-hash)
(eq-fn (hash-table-node-key node) key))
(let ([oldval (hash-table-node-value node)]
[left (hash-table-node-left-child node)]
[right (hash-table-node-right-child node)])
(cond
[(not left) (replace-node! right)]
[(not right) (replace-node! left)]
[else
(let find-leftmost ([parent node] [lnode right])
(let ([lc (hash-table-node-left-child lnode)])
(if lc
(find-leftmost lnode lc)
(let ([rc (hash-table-node-right-child lnode)])
(hash-table-node-left-child-set! parent rc)
(hash-table-node-left-child-set! lnode left)
(unless (eq? lnode right)
(hash-table-node-right-child-set! lnode right))
(replace-node! lnode)))))])
oldval)]
[(fix<= hash node-hash)
(search (hash-table-node-left-child node)
(lambda (n) (hash-table-node-left-child-set! node n)))]
[else
(search (hash-table-node-right-child node)
(lambda (n) (hash-table-node-right-child-set! node n)))]))
(not-found)))))
; vim:set syntax=scheme sw=2 expandtab: ; vim:set syntax=scheme sw=2 expandtab:

30
src/test-hash-table.rls
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@ -3,15 +3,29 @@
(define ht (make-hash-table)) (define ht (make-hash-table))
(hash-table-insert ht "test" 5) (define (foreach fn lst)
(hash-table-insert ht "a longer key" '(4 5 6)) (when (pair? lst)
(hash-table-insert ht '(9 8 7) "backwards") (fn (car lst))
(foreach fn (cdr lst))))
(let ([insert (lambda (x) (hash-table-insert ht x x))])
(foreach insert '(47 32 18 90 46 38 21 93 49 10 92 34 71)))
(values (values
(hash-table-lookup ht "test") (hash-table-remove ht 92)
(hash-table-lookup ht "no such key") (hash-table-remove ht 71)
(hash-table-lookup ht "a longer key") (hash-table-remove ht 49)
(hash-table-lookup ht '(7 8 9)) (hash-table-remove ht 46)
(hash-table-lookup ht '(9 8 7))) (hash-table-remove ht 47)
(hash-table-remove ht 21)
(hash-table-remove ht 30)
(hash-table-remove ht 34)
(hash-table-remove ht 18)
(hash-table-remove ht 32)
(hash-table-remove ht 90)
(hash-table-remove ht 10)
(hash-table-remove ht 38)
(hash-table-remove ht 93)
)
; vim:set syntax=scheme sw=2 expandtab: ; vim:set syntax=scheme sw=2 expandtab: