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13 lines
494 B
Racket
13 lines
494 B
Racket
#lang racket/base
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(require "racket.rkt")
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(provide (all-defined-out))
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(require "number.rkt")
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(define (resolve-length len-arg [stream #f] [parent #f])
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(cond
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[(not len-arg) #f]
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[(number? len-arg) len-arg]
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[(procedure? len-arg) (len-arg parent)]
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[(and parent (key? len-arg)) (ref parent len-arg)] ; treat as key into RStruct parent
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[(and stream (NumberT? len-arg)) (send len-arg decode stream)]
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[else (raise-argument-error 'resolveLength "fixed-size argument" len-arg)])) |