286 lines
7.9 KiB
Scheme
286 lines
7.9 KiB
Scheme
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; -*- Mode: Scheme; Syntax: Scheme; Package: Scheme; -*-
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; Copyright (c) 1994 by Richard Kelsey. See file COPYING.
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; Scheme48 reader modified to annotate pairs with source line and column
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; data.
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(define-record-type annotation
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(
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file
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row
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column
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)
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(form
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))
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(define $current-annotating-port (make-fluid #f))
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(define-syntax define-lap
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(lambda (exp rename compare)
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(let ((spec (cadr exp))
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(stuff (cddr exp)))
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`(define ,(car spec) (lap ,spec . ,stuff)))))
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(define-lap (annotated-cons car cdr annotation)
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(check-nargs= 3)
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(pop)
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(make-stored-object 3 pair)
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(return))
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(define (file-annotated-cons car cdr row column)
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(let* ((note (annotation-maker (fluid $current-annotating-port)
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row
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column))
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(pair (annotated-cons car cdr note)))
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(set-annotation-form! note pair)
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(make-immutable! note)
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(make-immutable! pair)
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pair))
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(define-lap (pair-annotation pair)
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(check-nargs= 1)
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(make-env 1)
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(local pair)
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(stored-object-length pair)
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(push)
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(literal 3)
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(=)
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(jump-if-false lose)
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(local pair)
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(stored-object-ref pair 2) ; this is the reason for the LAP
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(return)
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lose
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(false)
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(return))
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; A little Scheme reader.
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; Nonstandard things needed:
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; char->ascii, ascii->char (for dispatch table)
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; make-fluid, fluid (used only to implement ##)
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; reverse-list->string (ok to define as list->string of reverse)
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; really-string->symbol (ok to define this to be string->symbol)
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(define preferred-case
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(if (char=? (string-ref (symbol->string 't) 0) #\T)
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char-upcase
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char-downcase))
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(define close-paren (list 'close-paren))
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(define dot (string->symbol "."))
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(define (read-and-annotate port id)
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(let-fluid $current-annotating-port id
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(lambda ()
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(let loop ()
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(let ((form (sub-read port)))
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(cond ((eq? form dot)
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(error "\" . \" in illegal context"))
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((eq? form close-paren)
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;; Too many right parens.
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(loop))
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(else form)))))))
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(define (sub-read-carefully port)
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(let ((form (sub-read port)))
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(cond ((eof-object? form)
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(error "unexpected end of file"))
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((eq? form close-paren)
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(error "unexpected right parenthesis"))
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((eq? form dot)
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(error "unexpected \" . \""))
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(else form))))
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; Main dispatch
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(define (sub-read port)
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(let ((c (read-char port)))
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(if (eof-object? c)
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c
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((vector-ref read-dispatch-vector (char->ascii c))
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c port))))
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(define read-dispatch-vector
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(make-vector 256
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(lambda (c port)
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(error "illegal character read" c))))
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(define read-terminating?-vector
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(make-vector 256 #t))
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(define (set-standard-syntax! char terminating? reader)
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(vector-set! read-dispatch-vector (char->ascii char) reader)
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(vector-set! read-terminating?-vector (char->ascii char) terminating?))
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(let ((sub-read-whitespace
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(lambda (c port)
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c ;ignored
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(sub-read port))))
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(do ((i 0 (+ i 1)))
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((>= i (vector-length read-dispatch-vector)))
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(if (char-whitespace? (ascii->char i))
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(vector-set! read-dispatch-vector i sub-read-whitespace))))
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(let ((sub-read-constituent
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(lambda (c port)
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(parse-token (sub-read-token c port)))))
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(for-each (lambda (c)
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(set-standard-syntax! c #f sub-read-constituent))
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(string->list
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(string-append "!$%&*+-./0123456789:<=>?@^_~ABCDEFGHIJKLM"
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"NOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"))))
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; Usual read macros
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(define (set-standard-read-macro! c terminating? proc)
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(set-standard-syntax! c terminating? proc))
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(define (sub-read-list c port)
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(let* ((row (current-row port))
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(column (- (current-column port) 1)) ; to get the location of "("
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(form (sub-read port)))
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(cond ((eof-object? form)
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(error "end of file inside list -- unbalanced parentheses"))
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((eq? form close-paren) '())
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((eq? form dot)
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(let* ((last-form (sub-read-carefully port))
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(another-form (sub-read port)))
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(cond ((eq? another-form close-paren)
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last-form)
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(else
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(error "randomness after form after dot" another-form)))))
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(else
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(file-annotated-cons form (sub-read-list c port) row column)))))
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(set-standard-read-macro! #\( #t sub-read-list)
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(set-standard-read-macro! #\) #t
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(lambda (c port)
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c port
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close-paren))
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(set-standard-read-macro! #\' #t
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(lambda (c port)
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c
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(list 'quote (sub-read-carefully port))))
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(set-standard-read-macro! #\` #t
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(lambda (c port)
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c
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(list 'quasiquote (sub-read-carefully port))))
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(set-standard-read-macro! #\, #t
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(lambda (c port)
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c
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;; Do not beta-reduce this!
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(let* ((next (peek-char port))
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(marker (cond ((eof-object? next)
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(error "end of file after ,"))
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((char=? next #\@)
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(read-char port)
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'unquote-splicing)
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(else 'unquote))))
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(list marker
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(sub-read-carefully port)))))
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(set-standard-read-macro! #\" #t
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(lambda (c port)
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c ;ignored
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(let loop ((l '()) (i 0))
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(let ((c (read-char port)))
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(cond ((eof-object? c)
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(error "end of file within a string"))
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((char=? c #\\)
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(let ((c (read-char port)))
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(cond ((eof-object? c)
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(error "end of file within a string"))
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((or (char=? c #\\) (char=? c #\"))
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(loop (cons c l) (+ i 1)))
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(else
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(error "invalid escaped character in string" c)))))
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((char=? c #\")
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(reverse-list->string l i))
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(else
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(loop (cons c l) (+ i 1))))))))
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(set-standard-read-macro! #\; #t
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(lambda (c port)
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c ;ignored
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(gobble-line port)
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(sub-read port)))
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(define (gobble-line port)
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(let loop ()
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(let ((c (read-char port)))
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(cond ((eof-object? c) c)
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((char=? c #\newline) #f)
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(else (loop))))))
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(set-standard-read-macro! #\# #f
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(lambda (c port)
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c ;ignored
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(let* ((c (peek-char port))
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(c (if (eof-object? c)
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(error "end of file after #")
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(char-downcase c))))
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(cond ((char=? c #\f) (read-char port) #f)
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((char=? c #\t) (read-char port) #t)
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((char=? c #\\)
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(read-char port)
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(let ((c (peek-char port)))
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(cond ((eof-object? c)
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(error "end of file after #\\"))
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((char-alphabetic? c)
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(let ((name (sub-read-carefully port)))
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(cond ((= (string-length (symbol->string name)) 1)
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c)
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((assq name '((space #\space)
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(newline #\newline)))
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=> cadr)
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(else
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(error "unknown #\\ name" name)))))
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(else
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(read-char port)))))
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((char=? c #\()
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(read-char port)
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(list->vector (sub-read-list c port)))
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;; ## should evaluate to the last REP-loop result.
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((memq c '(#\b #\o #\d #\x #\i #\e))
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(let ((string (sub-read-token #\# port)))
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(or (string->number string)
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(error "unsupported number syntax" string))))
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; ((char=? c #\#) ; don't worry about this
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; (read-char port)
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; (make-last-value-expression))
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(else
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(error "unknown # syntax" c))))))
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; Tokens
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(define (sub-read-token c port)
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(let loop ((l (list (preferred-case c))) (n 1))
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(let ((c (peek-char port)))
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(cond ((or (eof-object? c)
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(vector-ref read-terminating?-vector (char->ascii c)))
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(reverse-list->string l n))
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(else
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(loop (cons (preferred-case (read-char port)) l)
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(+ n 1)))))))
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(define (parse-token string)
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(if (let ((c (string-ref string 0)))
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(or (char-numeric? c) (char=? c #\+) (char=? c #\-) (char=? c #\.)))
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(cond ((string->number string))
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((member string strange-symbol-names)
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(string->symbol string))
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((string=? string ".")
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dot)
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(else
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(error "unsupported number syntax" string)))
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(string->symbol string)))
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(define strange-symbol-names
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'("+" "-" "..." "1+" "-1+")) ;The latter two only for S&ICP support
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