45 lines
1.4 KiB
Racket
45 lines
1.4 KiB
Racket
;;; SPDX-License-Identifier: LGPL-3.0-or-later
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;;; SPDX-FileCopyrightText: Copyright © 2010-2021 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
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#lang racket/base
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;; Hash-table utilities that are not (yet) part of Racket
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(provide hash-set/remove
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hashset-member?
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hashset-add
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hashset-remove
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in-hashset-values)
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(require (only-in racket/set set seteq seteqv))
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(define (hash-set/remove ht key val [default-val #f] #:compare [compare equal?])
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(if (compare val default-val)
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(hash-remove ht key)
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(hash-set ht key val)))
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(define (hashset-member? ht key val)
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(define s (hash-ref ht key #f))
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(and s (hash-has-key? s val)))
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(define (make-hash-from-set-ctor ctor)
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(cond [(eq? ctor set) (hash)]
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[(eq? ctor seteq) (hasheq)]
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[(eq? ctor seteqv) (hasheqv)]
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[else (error 'hash-ctor-for-set-ctor "Cannot use hashset with set constructor ~v" ctor)]))
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(define (hashset-add ht key val #:set [set-ctor set])
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(define old-set (hash-ref ht key (lambda () (make-hash-from-set-ctor set-ctor))))
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(hash-set ht key (hash-set old-set val #t)))
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(define (hashset-remove ht k v)
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(define old (hash-ref ht k #f))
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(if old
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(let ((new (hash-remove old v)))
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(if (hash-empty? new)
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(hash-remove ht k)
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(hash-set ht k new)))
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ht))
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(define-syntax-rule (in-hashset-values ht key)
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(in-hash-keys (hash-ref ht key hash)))
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