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80 lines
2.6 KiB
Racket
80 lines
2.6 KiB
Racket
7 years ago
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#lang racket/base
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(require racket/generic
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(prefix-in b: racket/base)
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racket/dict
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racket/class
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racket/match)
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(provide (all-defined-out))
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(define-generics indexable
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(ref indexable i)
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(ref-set! indexable i v)
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#:defaults
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([hash? (define ref hash-ref)
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(define ref-set! hash-set!)]
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[object? (define (ref o i) (with-handlers ([exn:fail:object? (λ (exn) (hash-ref (get-field _hash o) i))]) (dynamic-get-field i o)))
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(define (ref-set! o i v) (with-handlers ([exn:fail:object? (λ (exn) (hash-set! (get-field _hash o) i v))]) (dynamic-set-field! i o v)))]))
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(module+ test
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(require rackunit)
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(define h (make-hash '((foo . 42))))
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(check-equal? (ref h 'foo) 42)
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(ref-set! h 'foo 85)
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(check-equal? (ref h 'foo) 85)
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(ref-set! h 'bar 121)
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(check-equal? (ref h 'bar) 121)
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(define o (make-object (class object% (super-new) (field [_hash (make-hash)][foo 42]))))
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(check-equal? (ref o 'foo) 42)
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(ref-set! o 'foo 100)
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(check-equal? (ref o 'foo) 100)
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(ref-set! o 'bar 121)
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(check-equal? (ref o 'bar) 121))
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(define (ref* c . is)
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(for/fold ([c c])
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([i (in-list is)])
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(ref c i)))
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(define (ref*-set! c . is+val)
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(match-define (list is ... i val) is+val)
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(ref-set! (apply ref* c is) i val))
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(require sugar/debug)
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(define (ref-set*! c . kvs)
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(for ([k (in-list kvs)]
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[v (in-list (cdr kvs))]
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[i (in-naturals)]
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#:when (even? i))
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(ref-set! c k v)))
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(module+ test
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(define h2 (make-hash (list (cons 'foo (make-hash (list (cons 'bar (make-hash '((zam . 42))))))))))
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(check-equal? (ref* h2 'foo 'bar 'zam) 42)
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(ref*-set! h2 'foo 'bar 'zam 89)
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(check-equal? (ref* h2 'foo 'bar 'zam) 89)
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(ref-set*! h2 'hi 1 'there 2)
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(check-equal? (ref h2 'hi) 1)
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(check-equal? (ref h2 'there) 2))
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(define-generics countable
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(length countable)
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#:defaults
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([list? (define length b:length)]
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[vector? (define length vector-length)]
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[string? (define length string-length)]
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[bytes? (define length bytes-length)]
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[dict? (define length dict-count)]
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[object? (define (length o) (with-handlers ([exn:fail:object? (λ (exn) 0)]) (b:length (get-field _list o))))]))
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(module+ test
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(require racket/list)
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(check-equal? (length (make-list 42 #f)) 42)
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(check-equal? (length (make-vector 42 #f)) 42)
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(check-equal? (length (make-string 42 #\x)) 42)
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(check-equal? (length (make-bytes 42 0)) 42)
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(check-equal? (length (map cons (range 42) (range 42))) 42)
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(check-equal? (length (make-object (class object% (super-new) (field [_list (make-list 42 #f)])))) 42)
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(check-equal? (length (make-object (class object% (super-new)))) 0))
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