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38 lines
1.2 KiB
Racket
38 lines
1.2 KiB
Racket
#lang racket/base
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(require racket/match racket/dict "int.rkt" "base.rkt")
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(provide (all-defined-out))
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(define (length-resolvable? x)
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(or (not x) (symbol? x) (xenomorphic? x) (procedure? x) (exact-nonnegative-integer? x)))
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(define (resolve-length x port [parent #f])
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(match x
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[#false #false]
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[(? exact-nonnegative-integer?) x]
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[(? procedure? proc) (proc parent)]
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[(? symbol? key) #:when parent (dict-ref parent key)]
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[(? x:int?) #:when port (decode x port)]
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[_ (raise-argument-error 'resolve-length "fixed-size argument" x)]))
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(define-values (PropertyDescriptor-prop PropertyDescriptor? _)
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(make-impersonator-property 'PropertyDescriptor))
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(define (PropertyDescriptor [opts (make-hash)])
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(define mh (make-hash))
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(for ([(k v) (in-hash opts)])
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(hash-set! mh k v))
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(impersonate-hash mh
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(λ (h k) (values k (λ (h k v) v)))
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(λ (h k v) (values k v))
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(λ (h k) k)
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(λ (h k) k)
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PropertyDescriptor-prop
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#true))
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(module+ test
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(require rackunit)
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(define pd (PropertyDescriptor))
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(hash-set! pd 'k 42)
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(check-equal? (hash-ref pd 'k) 42)
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(check-true (PropertyDescriptor? pd))
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(check-true (hash? pd))) |