961ece3ffe
unstable/contract: added rename-contract macro-debugger: switched to use interval-map for arrows svn: r17278
131 lines
4.4 KiB
Racket
131 lines
4.4 KiB
Racket
#lang scribble/manual
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@(require scribble/eval
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"utils.ss"
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(for-label unstable/skip-list
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scheme/contract
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scheme/dict
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scheme/base))
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@title[#:tag "skip-list"]{Skip Lists}
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@(define the-eval (make-base-eval))
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@(the-eval '(require unstable/skip-list))
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@(the-eval '(require scheme/dict))
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@defmodule[unstable/skip-list]
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@unstable[@author+email["Ryan Culpepper" "ryanc@plt-scheme.org"]]
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Skip lists are a simple, efficient data structure for mutable
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dictionaries with totally ordered keys. They were described in the
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paper ``Skip Lists: A Probabilistic Alternative to Balanced Trees'' by
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William Pugh in Communications of the ACM, June 1990, 33(6) pp668-676.
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A skip-list is a dictionary (@scheme[dict?] from
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@schememodname[scheme/dict]). It also supports extensions of the
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dictionary interface for iterator-based search and mutation.
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@defproc[(make-skip-list [=? (any/c any/c . -> . any/c)]
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[<? (any/c any/c . -> . any/c)])
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skip-list?]{
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Makes a new empty skip-list. The skip-list uses @scheme[=?] and @scheme[<?] to order keys.
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@examples[#:eval the-eval
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(define skip-list (make-skip-list = <))
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(skip-list-set! skip-list 3 'apple)
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(skip-list-set! skip-list 6 'cherry)
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(dict-map skip-list list)
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(skip-list-ref skip-list 3)
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(skip-list-remove! skip-list 6)
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(skip-list-count skip-list)
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]
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}
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@defproc[(skip-list? [v any/c])
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boolean?]{
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Returns @scheme[#t] if @scheme[v] is a skip-list, @scheme[#f]
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otherwise.
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}
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@deftogether[[
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@defproc[(skip-list-ref [skip-list skip-list?]
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[key any/c]
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[default any/c (lambda () (error ....))])
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any/c]
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@defproc[(skip-list-set! [skip-list skip-list?]
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[key any/c]
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[value any/c])
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void?]
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@defproc[(skip-list-remove! [skip-list skip-list?]
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[key any/c])
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void?]
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@defproc[(skip-list-count [skip-list skip-list?])
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exact-nonnegative-integer?]
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@defproc[(skip-list-iterate-first [skip-list skip-list?])
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(or/c skip-list-iter? #f)]
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@defproc[(skip-list-iterate-next [skip-list skip-list?]
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[iter skip-list-iter?])
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(or/c skip-list-iter? #f)]
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@defproc[(skip-list-iterate-key [skip-list skip-list?]
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[iter skip-list-iter?])
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any/c]
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@defproc[(skip-list-iterate-value [skip-list skip-list?]
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[iter skip-list-iter?])
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any/c]]]{
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Implementations of @scheme[dict-ref], @scheme[dict-set!],
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@scheme[dict-remove!], @scheme[dict-count],
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@scheme[dict-iterate-first], @scheme[dict-iterate-next],
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@scheme[dict-iterate-key], and @scheme[dict-iterate-value],
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respectively.
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}
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@deftogether[[
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@defproc[(skip-list-iterate-greatest/<? [skip-list skip-list?]
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[key any/c])
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(or/c skip-list-iter? #f)]
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@defproc[(skip-list-iterate-greatest/<=? [skip-list skip-list?]
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[key any/c])
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(or/c skip-list-iter? #f)]
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@defproc[(skip-list-iterate-least/>? [skip-list skip-list?]
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[key any/c])
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(or/c skip-list-iter? #f)]
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@defproc[(skip-list-iterate-least/>=? [skip-list skip-list?]
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[key any/c])
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(or/c skip-list-iter? #f)]]]{
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Return the position of, respectively, the greatest key less than
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@scheme[key], the greatest key less than or equal to @scheme[key], the
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least key greater than @scheme[key], and the least key greater than or
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equal to @scheme[key].
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}
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@deftogether[[
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@defproc[(skip-list-iterate-set-key! [skip-list skip-list?]
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[iter skip-list-iter?]
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[key any/c])
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void?]
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@defproc[(skip-list-iterate-set-value! [skip-list skip-list?]
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[iter skip-list-iter?]
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[value any/c])
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void?]]]{
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Set the key and value, respectively, at the position @scheme[iter] in
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@scheme[skip-list].
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@bold{Warning:} Changing a position's key to be less than its
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predecessor's key or greater than its successor's key results in an
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out-of-order skip-list, which may cause comparison-based operations to
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behave incorrectly.
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}
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@defproc[(skip-list-iter? [v any/c])
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boolean?]{
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Returns @scheme[#t] if @scheme[v] represents a position in a
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skip-list, @scheme[#f] otherwise.
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}
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