761054890d
to let lexers say "call me again before you change the buffer" also, use this in the 2d lexer
39 lines
1.3 KiB
Racket
39 lines
1.3 KiB
Racket
#lang racket/base
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(require racket/contract/base
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unstable/options)
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(provide lexer/c (struct-out dont-stop))
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(struct dont-stop (val) #:transparent)
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(define lexer/c
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(option/c
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(or/c (->i ([in (and/c input-port? port-counts-lines?)])
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(values [txt any/c]
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[type symbol?]
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[paren (or/c symbol? #f)]
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[start (or/c exact-positive-integer? #f)]
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[end (start type) (end/c start type)]))
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(->i ([in (and/c input-port? port-counts-lines?)]
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[offset exact-nonnegative-integer?]
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[mode (not/c dont-stop?)])
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(values [txt any/c]
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[type symbol?]
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[paren (or/c symbol? #f)]
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[start (or/c exact-positive-integer? #f)]
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[end (start type) (end/c start type)]
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[backup exact-nonnegative-integer?]
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[new-mode any/c])))
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#:tester (λ (x) (and (procedure? x)
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(or (procedure-arity-includes? x 1)
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(procedure-arity-includes? x 3))))))
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(define (end/c start type)
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(cond
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[(equal? 'eof type)
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(or/c exact-positive-integer? #f)]
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[start
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(and/c exact-positive-integer?
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(>/c start))]
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[else
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#f]))
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