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30 lines
730 B
Racket
30 lines
730 B
Racket
#lang restructure/racket
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(require "stream.rkt")
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(provide (all-defined-out))
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#|
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approximates
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https://github.com/mbutterick/restructure/blob/master/src/Optional.coffee
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|#
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(define-subclass Streamcoder (Optional type [condition #t])
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(define (resolve-condition parent)
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(if (procedure? condition)
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(condition parent)
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condition))
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(define/augment (decode stream parent)
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(when (resolve-condition parent)
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(send type decode stream parent)))
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(define/override (size [val #f] [parent #f])
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(if (resolve-condition parent)
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(send type size val parent)
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0))
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(define/augment (encode stream val parent)
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(when (resolve-condition parent)
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(send type encode stream val parent))))
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