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15 lines
574 B
Racket
15 lines
574 B
Racket
#lang racket/base
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(require racket/match racket/dict "number.rkt" "helper.rkt" "generic.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)])) |