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beautiful-racket/beautiful-racket-lib/br/reader-utils.rkt

44 lines
2.7 KiB
Racket

#lang racket/base
(require (for-syntax racket/base racket/syntax br/syntax) br/define syntax/strip-context)
(provide (all-defined-out))
(define (test-reader read-syntax-proc str)
(syntax->datum (read-syntax-proc #f (open-input-string str))))
;; `define-read-functions` simplifies support for the standard reading API,
;; which asks for `read` and `read-syntax`.
;; in general, `read` is just the datum from the result of `read-syntax`.
(define-macro (define-read-and-read-syntax (PATH PORT) BODY ...)
(let ([internal-prefix (gensym)])
(with-syntax ([READ (datum->syntax caller-stx 'read)]
[READ-SYNTAX (datum->syntax caller-stx 'read-syntax)]
;; use prefixed names to prevent namespace collisions with possibly existing `read` & `read-syntax`
[INTERNAL-READ (format-id #'here "~a-~a" internal-prefix 'read)]
[INTERNAL-READ-SYNTAX (format-id #'here "~a-~a" internal-prefix 'read-syntax)])
#'(begin
(provide (rename-out [INTERNAL-READ READ]
[INTERNAL-READ-SYNTAX READ-SYNTAX]))
(define (calling-site-function PATH PORT)
BODY ...) ; don't care whether this produces datum or syntax
(define INTERNAL-READ-SYNTAX
(procedure-rename (λ (path port) ; rename proc so it looks right in the REPL (otherwise retains internal prefix name)
;; because `read-syntax` must produce syntax
;; coerce a datum result to syntax if needed (à la `with-syntax`)
(define result-syntax (let ([output (calling-site-function path port)])
(if (syntax? output)
output
(datum->syntax #f output))))
;; because `read-syntax` must produce syntax without context
;; see http://docs.racket-lang.org/guide/hash-lang_reader.html
;; "a `read-syntax` function should return a syntax object with no lexical context"
(strip-context result-syntax)) 'READ-SYNTAX))
(define INTERNAL-READ
(procedure-rename (λ (port)
; because `read` must produce a datum
(let ([output (calling-site-function #f port)])
(if (syntax? output)
(syntax->datum output)
output))) 'READ))))))