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37 lines
1.7 KiB
Racket
37 lines
1.7 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base) syntax/strip-context)
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(provide define-read-functions)
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;; `define-read-functions` simplifies support for the standard reading API,
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;; which asks for `read` and `read-syntax`.
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;; in general, `read` is just the datum from the result of `read-syntax`.
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(define-syntax (define-read-functions use-site-stx)
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(syntax-case use-site-stx ()
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[(_ (PATH PORT) BODY ...)
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(with-syntax ([READ (datum->syntax use-site-stx 'read)]
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[READ-SYNTAX (datum->syntax use-site-stx 'read-syntax)])
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#'(begin
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(provide READ READ-SYNTAX)
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(define (use-site-read-function PATH PORT)
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BODY ...) ; don't care whether this produces datum or syntax
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(define (READ-SYNTAX path port)
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;; because `read-syntax` must produce syntax
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;; coerce a datum result to syntax if needed (à la `with-syntax`)
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(define result-syntax (let ([output (use-site-read-function path port)])
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(if (syntax? output)
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output
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(datum->syntax #f output))))
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;; because `read-syntax` must produce syntax without context
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;; see http://docs.racket-lang.org/guide/hash-lang_reader.html
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;; "a `read-syntax` function should return a syntax object with no lexical context"
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(strip-context result-syntax))
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(define (READ port)
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; because `read` must produce a datum
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(let ([output (use-site-read-function #f port)])
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(if (syntax? output)
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(syntax->datum output)
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output)))))]))
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