1054 lines
38 KiB
Scheme
1054 lines
38 KiB
Scheme
;;; Copyright (C) Peter McGoron 2024
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;;; This program is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation, version 3 of the License.
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;;;
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;;; This program is distributed in the hope that it will be useful,
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;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with this program. If not, see <https://www.gnu.org/licenses/>.
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;;; R7RS reader. This is the lexer-parser end, so it returns tokens and
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;;; not concrete objects.
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;;;
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;;; Notes:
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;;;
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;;; Port stores datum labels. Datum labels are stored for the entirety of
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;;; a READ: this is to emulate MIT Scheme, which allows for datum labels
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;;; outside of the datum that the label appears in.
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;;;
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;;; The reader does not return Scheme data: it returns annotated data
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;;; containing the source location, datum label number, resolved datum
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;;; label pointer. This is for advanced syntax systems.
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;;;
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;;; How datum labels could work:
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;;;
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;;; When encountering #[number]=, allocate a datum label and assign it
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;;; nothing. Then call READ after "=", and destructively update the
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;;; datum label with the resulting datum. A pass over the new read
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;;; structure to convert it to regular Scheme data will resolve the
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;;; indirection.
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;;;
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;;; All tokens are procedure-encapsulated objects, since the reader should
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;;; never return a literal procedure. Each procedure has a TYPE message.
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(load "chez-compat.scm")
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(load "util.scm")
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(load "set.scm")
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(load "linked-list.scm")
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;;; My text editor cannot parse Scheme's character syntax.
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(define %bol #\()
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(define %eol #\))
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Port reader wrapper
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;
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(define port->read-function
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(lambda (port)
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(lambda ()
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(read-char port))))
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(define string->read-function
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(lambda (str)
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(let ((i -1)
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(length (string-length str)))
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(lambda ()
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(set! i (+ i 1))
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(if (>= i length)
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#f
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(string-ref str i))))))
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;;; READ:
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;;;
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;;; Stream readers contain mutable state. This is the case-folding mode
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;;; and the current list of datum labels.
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;;;
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;;; (POS): Return (LIST FILENAME LINE-NUMBER OFFSET).
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;;; (READ): Read the next character in the stream. Returns #F on EOF.
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;;; (PUSH CHAR): Push CHAR such that it will be the next character read
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;;; when (READ) is called.
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;;; (PEEK): Read character, push it back, and return it.
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;;; (FOLD-CASE?): Returns a boolean if case folding is enabled.
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;;; (FOLD-CASE! BOOL): Sets the case folding to BOOL.
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(define port->read
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(lambda (read-function filename . location)
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(let ((line-number (if (null? location)
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1
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(car location)))
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(offset (if (null? location)
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0
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(cadr location)))
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(pushback-buffer '())
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(datum-labels '())
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(fold-case? #f))
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(letrec ((update-position!
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(lambda (ch)
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(cond
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((eqv? ch #\newline)
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(set! line-number (+ 1 line-number)) (set! offset 0))
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;; OFFSET is sometimes set to #F to denote an unknown
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;; offset.
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(offset (set! offset (+ 1 offset))))))
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(location
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(lambda () (list filename line-number offset)))
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(set-datum-label!
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(lambda (label value)
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(set! datum-labels
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(car (smap:insert datum-labels label value)))))
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(get-datum-label
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(lambda (label)
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(smap:search datum-labels label)))
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(clear-datum-labels!
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(lambda ()
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(set! datum-labels '())))
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(dump-mutable
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(lambda ()
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(list datum-labels fold-case?)))
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(restore-mutable!
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(lambda (state)
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(set! datum-labels (car state))
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(set! fold-case? (cadr state))))
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(process
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(lambda (ch)
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(update-position! ch)
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(cond
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((or (eof-object? ch) (not ch)) ch)
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(fold-case? (char-downcase ch))
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(else ch))))
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(port
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(lambda (op . args)
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;; TODO: turn into string map?
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(cond
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((eq? op 'location) (location))
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((eq? op 'read)
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(process
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(if (null? pushback-buffer)
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(read-function)
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(let ((ch (car pushback-buffer)))
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(set! pushback-buffer (cdr pushback-buffer))
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ch))))
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((eq? op 'peek)
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(let ((ch (port 'read)))
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(port 'push ch)
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ch))
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((eq? op 'push)
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(let ((ch (car args)))
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(if (eqv? ch #\newline)
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(begin
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(set! line-number (- line-number 1))
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(set! offset #f))
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(set! offset (- offset 1)))
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(set! pushback-buffer (cons ch pushback-buffer))))
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((eq? op 'fold-case?) fold-case?)
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((eq? op 'fold-case!) (set! fold-case? (car args)))
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((eq? op 'set-datum-label!) (apply set-datum-label! args))
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((eq? op 'get-datum-label) (apply get-datum-label args))
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((eq? op 'clear-datum-labels!) (apply clear-datum-labels! args))
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((eq? op 'dump-mutable) (apply dump-mutable args))
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((eq? op 'restore-mutable!) (apply restore-mutable! args))
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(else (error 'read->port 'invalid (cons op args)))))))
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port))))
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(define ident->read
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(lambda (location ident)
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(apply port->read (string->read-function (ident 'value))
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location)))
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;;; ;;;;;;;;;;;;;;
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;;; Character maps
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;;; ;;;;;;;;;;;;;;
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(define integer<=>
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(lambda (x y)
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(cond
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((< x y) '<)
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((= x y) '=)
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(else '>))))
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;;; Comparison on characters extended to #F, which is less than all
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;;; characters.
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(define char*<=>
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(lambda (x y)
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(cond
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((and (not x) y) '<)
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((and x (not y)) '>)
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((and (not x) (not y) '=))
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(else (integer<=> (char->integer x)
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(char->integer y))))))
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(define %charmap:<=> (set:<=>-to-map char*<=>))
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(define %charmap:update (set:update %charmap:<=>))
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(define charmap:update (map:update %charmap:update))
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(define charmap:insert (map:insert %charmap:update))
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(define charmap:search (map:search %charmap:<=>))
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;;; ;;;;;;;;;;;;;;;;;;;;;;
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;;; Readtable constructors
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;;;
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;;; Readtables are composed of a CHARMAP, which is a map from characters
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;;; to actions, and a DEFAULT-ACTION, which is taken when there is no
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;;; match in CHARMAP.
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;;;
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;;; An "action" is a procedure that takes four arguments:
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;;;
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;;; TABLE: The current table.
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;;; CHAR: The character that was matched against the CHARMAP in TABLE.
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;;; ACC: An arbitrary "accumulator" value that is different depending
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;;; on the readtable in question.
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;;; PORT: A port reader object.
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;;; ;;;;;;;;;;;;;;;;;;;;;;
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;;; (READTABLE:NEW DEFAULT-ACTION CHARMAP)
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(define readtable:new cons)
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(define %readtable:default-action car)
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(define %readtable:charmap cdr)
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;;; Run the action in TABLE assigned to CHAR, or the default action of
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;;; TABLE if there is no entry for CHAR.
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(define readtable:act
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(lambda (table char acc port)
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(let ((node (charmap:search (%readtable:charmap table)
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char)))
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(let ((action (if (null? node)
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(%readtable:default-action table)
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(map:val node))))
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(action table char acc port)))))
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;;; Run the action in TABLE with the next character from PORT.
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(define readtable:next
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(lambda (table acc port)
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(readtable:act table (port 'read) acc port)))
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;;; Return a new readtable where CHAR is bound to ACTION.
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(define readtable:update
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(lambda (table chars action)
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(let ((chars (if (pair? chars)
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chars
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(list chars))))
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(fold (lambda (char table)
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(readtable:new (%readtable:default-action table)
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(car (charmap:insert
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(%readtable:charmap table) char action))))
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table
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chars))))
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;;; Construct new readtable with no characters in its map and
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;;; DEFAULT-ACTION as the default action.
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(define readtable:empty/default
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(lambda (default-action)
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(readtable:new default-action '())))
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;;; Each value in FUNCTIONS is a list (PROCEDURE ARGS...) which is called
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;;; like (PROCEDURE TABLE ARGS...) and returns a table.
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(define readtable:process
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(lambda (table . functions)
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(fold (lambda (function table)
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(apply (car function) table (cdr function)))
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table
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functions)))
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;;; ;;;;;;;;;;;;;;;;;;
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;;; Default actions
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;;; ;;;;;;;;;;;;;;;;;;
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;;; Return an error.
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(define readtable:error
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(lambda emsg
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(lambda (table char acc port)
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(error emsg char acc table port))))
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;;; Discard the current character and continue reading the readtable.
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(define readtable:skip
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(lambda (table char acc port)
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(readtable:act table (port 'read) acc port)))
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;;; Discard char and return constant.
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(define readtable:return
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(lambda (return)
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(lambda (table char acc port)
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return)))
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;;; Jump to a new readtable, discard it's return, and continue reading
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;;; in the table.
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(define readtable:jump-discard
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(lambda (newtable)
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(lambda (oldtable char acc port)
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(readtable:act newtable (port 'read) '() port)
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(readtable:act oldtable (port 'read) acc port))))
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;;; Jump to a new readtable with the same characters.
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(define readtable:jump
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(lambda (newtable)
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(lambda (oldtable char acc port)
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(readtable:act newtable char acc port))))
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;;; Jump to a new readtable, reading the new character, with the old
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;;; readtable as ACC.
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(define readtable:next/old-as-acc
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(lambda (newtable)
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(lambda (oldtable __ _ port)
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(readtable:next newtable oldtable port))))
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;;; Jump to a new readtable, reading the new character.
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(define readtable:jump/next
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(lambda (newtable)
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(lambda (oldtable _ acc port)
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(readtable:next newtable acc port))))
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;;; ;;;;;;;;;;;;;;;;;
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;;; Identifier reader
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;;; ;;;;;;;;;;;;;;;;;
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(define read:ident
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(lambda (name location)
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(lambda (op . args)
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(cond
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((eq? op 'type) 'ident)
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((eq? op 'value) name)
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(else (error 'read:ident "invalid operation" op args))))))
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(define read:ident-builder
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(lambda (location . start-char)
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(let ((char-list (linked-list:new)))
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(if (not (null? start-char))
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(char-list 'push (car start-char)))
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(lambda (op . args)
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(cond
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((eq? op 'finalize->ident)
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(read:ident (list->string (char-list 'to-list)) location))
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(else (apply char-list op args)))))))
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;;; Push back CHAR and return ACC.
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(define readtable:return-acc-as-ident
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(lambda (table char acc port)
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(port 'push char)
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(acc 'finalize->ident)))
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;;; Push CHAR to ACC and continue reading from TABLE.
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(define readtable:push-char
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(lambda (table char acc port)
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(acc 'push-tail char)
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(readtable:act table (port 'read) acc port)))
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;;; Define a readtable that constructs an identifier by accepting all
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;;; characters that are not listed.
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(define readtable:exclude-from-identifiers
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(lambda (table excluded)
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(fold (lambda (char table)
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(readtable:update table char readtable:return-acc-as-ident))
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table
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excluded)))
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;;; ASCII whitespace.
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(define readtable:ASCII-whitespace
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(list #\newline
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#\space
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(integer->char #x09)
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(integer->char #x0B)
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(integer->char #x0C)
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(integer->char #x0D)))
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;;; Readtable for identifiers.
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(define readtable:identifier
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(readtable:process
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(readtable:empty/default readtable:push-char)
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(list readtable:exclude-from-identifiers
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readtable:ASCII-whitespace)
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(list readtable:exclude-from-identifiers
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(list #\| %bol %eol #\' #\; #f))))
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;;; Read an identifier starting with CHAR.
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(define readtable:read-ident
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(lambda (table char acc port)
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(readtable:act readtable:identifier
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(port 'read)
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(read:ident-builder (port 'location)
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char)
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port)))
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;;; ;;;;;;;;;;;;;;;;;;;;
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;;; Comments and whitespace reader
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;;; ;;;;;;;;;;;;;;;;;;;;
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;;; Readtable for a line comment.
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(define readtable:read-to-newline
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(readtable:process
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(readtable:empty/default readtable:skip)
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(list readtable:update #\newline (readtable:return #f))))
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;;; ;;;;;;;;;;;
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;;; List reader
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;;;
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;;; The reader updates the previous readtable to handle ). This means
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;;; that this read table does not have to handle end-of-line, whitespace,
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;;; etc.
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;;; ;;;;;;;;;;;
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;;; Read the end of an improper list.
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(define readtable:read-improper-cdr
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(lambda (table acc port)
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(let ((val
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(readtable:act (readtable:update table
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%eol
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(readtable:error
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'read-improper-cdr
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"proper list must have cdr"))
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(port 'read)
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#f
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port)))
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(acc 'set-cdr! val)
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(let ((table (readtable:process
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(readtable:empty/default (readtable:error
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'read-improper-cdr
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"improper list has 1 cdr"))
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(list readtable:update
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readtable:ASCII-whitespace
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readtable:skip)
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(list readtable:update %eol
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(lambda dummy 'end-of-list)))))
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(readtable:act table (port 'read) acc port)))))
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;;; Generic reader loop for a list. It takes as input the table that has
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;;; already been updated with end of list and improper list handlers.
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(define readtable:read-list-loop
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(lambda (table port)
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(let ((acc (linked-list:new)))
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(letrec ((loop
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(lambda ()
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(let ((value (readtable:act table
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(port 'read)
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acc
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port)))
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(cond
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((eqv? value 'end-of-list) (acc 'to-list))
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(else (acc 'push-tail value)
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(loop)))))))
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(loop)))))
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;;; Readtable for a list, generic to proper and improper list
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;;; readers.
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(define readtable:table-for-list
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(lambda (oldtable on-dot)
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(readtable:process
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oldtable
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(list readtable:update %eol (readtable:return 'end-of-list))
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(list readtable:update #\.
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(lambda (table char acc port)
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(let ((entire-identifier (readtable:read-ident
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table
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char
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#f
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port)))
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(if (equal? entire-identifier ".")
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(on-dot table acc port)
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entire-identifier)))))))
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;;; Read a proper or improper list.
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(define readtable:read-list
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(lambda (oldtable _ __ port)
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(readtable:read-list-loop (readtable:table-for-list
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oldtable
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readtable:read-improper-cdr)
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port)))
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;;; Read strictly a proper list. This assumes that BOL has been read.
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(define readtable:read-proper-list
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(lambda (table port)
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(readtable:read-list-loop (readtable:table-for-list
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table
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(readtable:error
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'read-proper-list
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"expected proper list"))
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port)))
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(define readtable:expect-proper-list
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(lambda (table port)
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(if (not (eqv? (port 'read) %bol))
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(error 'expect-port-list 'no-list-found)
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(readtable:read-proper-list table port))))
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Implementation of a Pratt parser. In a Pratt parser, all tokens are
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;;; "operators" with "precedence".
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;;;
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;;; Since Pratt parsers are implemented in terms of procedures, they can
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;;; parse any grammar.
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;;;
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;;; This file implements the algorithm found in:
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;;;
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;;; van de Vanter, Michael L. "A Formalization and Correctness Proof of
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;;; the CGOL Language System." (Master's Thesis). MIT Laboratory for
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;;; Computer Science Technical Report MIT-LCS-TR-147 (Cambridge,
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;;; Massachusetts). 1975. https://hdl.handle.net/1721.1/149442.
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;;; (PRATT:OPERATOR PRECEDENCE PROCEDURE)
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;;; constructs a description of an operator.
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;;;
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;;; PRECEDENCE is an exact number describing the precedence of the
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;;; operator, and for portability should only be an integer.
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;;;
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;;; (The special EOF operator, which always exists, has negative
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;;; infinity precedence.)
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;;;
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;;; PROCEDURE is of the form (PROCEDURE OPERATORS LEFT TOKEN READER).
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;;; OPERATORS is the operators map.
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;;; LEFT is a PRATT:TOKEN, which was to the left of the operator.
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;;; TOKEN is the token read from the reader wit the same type.
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;;; READER is a reader object.
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;;;
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;;; PROCEDURE consumes tokens to obtain the
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;;; right hand side of its expression. PROCEDURE produces a PRATT:TOKEN.
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(define pratt:operator cons)
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(define pratt:precedence car)
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|
(define pratt:procedure cdr)
|
|
|
|
(define pratt:search-token
|
|
(lambda (operators token)
|
|
(smap:search operators (symbol->string (token 'type)))))
|
|
|
|
;;; Parse a stream from READER, where the precedence limit is specified as
|
|
;;; BINDING-POWER. If BINDING-POWER is #F, then there is no precedence
|
|
;;; limit. Operators are read from OPERATORS, which is a SMAP.
|
|
(define pratt
|
|
(lambda (operators binding-power reader)
|
|
(letrec
|
|
((loop
|
|
(lambda (left)
|
|
(let ((token (reader 'peek)))
|
|
(let ((operator (pratt:search-token operators token)))
|
|
(if (null? next-operator)
|
|
(error 'pratt 'unknown-operator token
|
|
operators binding-power reader))
|
|
(if (and binding-power
|
|
(>= (pratt:precedence operator)
|
|
binding-power))
|
|
left
|
|
(parse operator left (reader 'read) reader))))))
|
|
(parse
|
|
(lambda (operator left token reader)
|
|
(loop ((pratt:procedure operator)
|
|
operators
|
|
left
|
|
token
|
|
reader)))))
|
|
;; Read the first token.
|
|
(let ((token (reader 'read)))
|
|
(let ((operator (pratt:search-token operators token)))
|
|
(if (null? operator)
|
|
(error 'pratt 'unknown-operator token
|
|
operators binding-power reader))
|
|
(parse operator #f token reader))))))
|
|
|
|
;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;;; Math reader.
|
|
;;;
|
|
;;; Scheme numbers are a kludge. A proper LISP would either represent
|
|
;;; numbers as
|
|
;;;
|
|
;;; (+ 4 (*i 6)) or (@ (. 12 34) 2) or (e 12 3) etc.
|
|
;;;
|
|
;;; or just bite the bullet and include a full infix expression parser.
|
|
;;;
|
|
;;; This is a full infix expression parser. It will parse expressions
|
|
;;; such as SIN(X) or X * 5I/6. Identifiers and functions are any Scheme
|
|
;;; object.
|
|
;;;
|
|
;;; The math reader can be invoked using #MATH(expr). EXPR is an infix
|
|
;;; mathematical expression. #PREFIX(expr) reads EXPR in the normal
|
|
;;; reader. All other hash identifiers are unsupported in #MATH.
|
|
|
|
;;; The basic number reader. The basic syntax is
|
|
;;;
|
|
;;; PREFIXES* SIGN? (RADIX+ ("." RADIX+)? | "." RADIX+) ("e" RADIX+)? "i"?
|
|
;;; Prefixes are handled by the "#" reader.
|
|
|
|
;;; Incremental builder for a number, driven by the lexer.
|
|
;;; TODO: how will this be turned into a number, in the end?
|
|
(define read:number-builder
|
|
(lambda (radix-table)
|
|
(let ((main '())
|
|
(decimal '())
|
|
(exp-char #f)
|
|
(exp-digits '())
|
|
(imaginary? #f)
|
|
(current-part 'main)
|
|
(exactness #f))
|
|
(let ((append-part
|
|
(lambda (char)
|
|
(cond
|
|
((eq? current-part 'main)
|
|
(set! main (cons char main)))
|
|
((eq? current-part 'decimal)
|
|
(set! decimal (cons char decimal)))
|
|
((eq? current-part 'exp)
|
|
(set! exp-digits (cons char exp-digits)))))))
|
|
(lambda (op . args)
|
|
(cond
|
|
((eq? op 'finalize)
|
|
(if (not exactness)
|
|
(set! exactness 'exact))
|
|
(list 'number-builder
|
|
main exactness decimal exp-char exp-digits imaginary?))
|
|
((eq? op 'exactness!) (set! exactness (car args)))
|
|
((eq? op 'radix-table!) (set! radix-table (car args)))
|
|
((eq? op 'set-imaginary!)
|
|
(set! imaginary? #t))
|
|
((eq? op 'set-decimal!)
|
|
(if (not exactness)
|
|
(set! exactness 'inexact))
|
|
;;
|
|
(if (not (eq? current-part 'main))
|
|
(error 'number-builder "cannot set to decimal" current-part)
|
|
(set! current-part 'decimal)))
|
|
((eq? op 'set-exponential!)
|
|
(if (not exactness)
|
|
(set! exactness 'inexact))
|
|
;;
|
|
(if (eq? current-part 'exp)
|
|
(error 'number-builder "cannot set to exponential"))
|
|
(set! current-part 'exp)
|
|
(set! exp-char (car args)))
|
|
;;
|
|
((eq? op 'radix-table) radix-table)
|
|
(else (append-part op))))))))
|
|
|
|
(define readtable:return-number
|
|
(lambda (_ char acc port)
|
|
(port 'push char)
|
|
(acc 'finalize)))
|
|
|
|
;;; Main lexer for number table.
|
|
(define readtable:number-main-table
|
|
(readtable:process
|
|
(readtable:empty/default readtable:return-number)
|
|
(list readtable:update #\.
|
|
(lambda (table char number-builder port)
|
|
(number-builder 'set-decimal!)
|
|
(readtable:next table
|
|
number-builder
|
|
port)))
|
|
(list readtable:update (list #\e #\s #\f #\d #\l)
|
|
(lambda (table char number-builder port)
|
|
(number-builder 'set-exponential! char)
|
|
(readtable:next table
|
|
number-builder
|
|
port)))
|
|
(list readtable:update #\_ readtable:skip)
|
|
(list readtable:update #\i
|
|
(lambda (table char number-builder port)
|
|
(number-builder 'set-imaginary!)
|
|
(number-builder 'finalize)))))
|
|
|
|
;;; Generate a lexer given a list of numbers in the radix.
|
|
(define readtable:for-radix
|
|
(lambda (radix-list)
|
|
(readtable:process
|
|
readtable:number-main-table
|
|
(list readtable:update radix-list
|
|
(lambda (table char number-builder port)
|
|
(number-builder char)
|
|
(readtable:next table number-builder port))))))
|
|
|
|
(define readtable:for-bin
|
|
(readtable:for-radix '(#\0 #\1)))
|
|
(define readtable:for-oct
|
|
(readtable:for-radix '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7)))
|
|
(define readtable:for-dec
|
|
(readtable:for-radix '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9)))
|
|
(define readtable:for-hex
|
|
(readtable:for-radix '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
|
|
#\a #\b #\c #\d #\e #\f)))
|
|
|
|
;;; Read the sign at the start of a number.
|
|
(define readtable:read-sign
|
|
(readtable:process
|
|
(readtable:empty/default
|
|
(lambda (_ char number-builder port)
|
|
(readtable:act (number-builder 'radix-table)
|
|
char
|
|
number-builder
|
|
port)))
|
|
(list readtable:update (list #\+ #\-)
|
|
(lambda (_ char number-builder port)
|
|
(number-builder 'sign! char)
|
|
(readtable:next (number-builder 'radix-table)
|
|
number-builder
|
|
port)))
|
|
(list readtable:update #\_ readtable:skip)))
|
|
|
|
(define readtable:read-prefix-char
|
|
(let ((act (lambda args
|
|
(lambda (_ char number-builder port)
|
|
(apply number-builder args)
|
|
(readtable:next readtable:read-number-prefix
|
|
number-builder
|
|
port)))))
|
|
(readtable:process
|
|
(readtable:empty/default (readtable:error "invalid prefix"))
|
|
(list readtable:update #\i (act 'exactness! 'inexact))
|
|
(list readtable:update #\e (act 'exactness! 'exact))
|
|
(list readtable:update #\b (act 'radix-table! readtable:for-bin))
|
|
(list readtable:update #\o (act 'radix-table! readtable:for-oct))
|
|
(list readtable:update #\d (act 'radix-table! readtable:for-dec))
|
|
(list readtable:update #\x (act 'radix-table! readtable:for-hex)))))
|
|
|
|
(define readtable:read-number-prefix
|
|
(readtable:process
|
|
(readtable:empty/default (readtable:jump readtable:read-sign))
|
|
(list readtable:update #\# (readtable:jump/next readtable:read-prefix-char))))
|
|
|
|
;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;;; Reader for stuff that start with "#"
|
|
;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
(define readtable:digits
|
|
(list #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9))
|
|
|
|
(define readtable:vector
|
|
(lambda (_ __ toplevel port)
|
|
(list 'vector (readtable:read-proper-list toplevel port))))
|
|
|
|
;;; Block comment reader.
|
|
;;;
|
|
;;; The outermost block comment reader is passed the toplevel reader as
|
|
;;; ACC. When the outermost block is finished, it will tail-call ACC.
|
|
;;; (It is basically the continuation of the reader.)
|
|
;;;
|
|
;;; When a nested block comment is found, it is passed #F as ACC, which
|
|
;;; it will not call. It will return an unspecified value.
|
|
;;;
|
|
;;; Since the read tables are not procedures, references to other tables
|
|
;;; in the same LETREC declaration must be protected with explicit LAMBDAs.
|
|
;;; Macros could make this much easier to read.
|
|
(define readtable:block-comment
|
|
(letrec ((potential-end
|
|
(readtable:process
|
|
(readtable:empty/default
|
|
(lambda (this char acc port) (readtable:act
|
|
loop
|
|
char
|
|
acc
|
|
port)))
|
|
(list readtable:update #\#
|
|
(lambda (this char acc port)
|
|
(if acc
|
|
(readtable:next acc #f port))))))
|
|
(potential-start
|
|
(readtable:process
|
|
(readtable:empty/default
|
|
(lambda (this char acc port) (readtable:act
|
|
loop
|
|
char
|
|
acc
|
|
port)))
|
|
(list readtable:update #\|
|
|
(lambda (this char acc port)
|
|
(readtable:next loop #f port)
|
|
(readtable:next loop acc port)))))
|
|
(loop
|
|
(readtable:process
|
|
(readtable:empty/default readtable:skip)
|
|
(list readtable:update #\#
|
|
(lambda (this char acc port)
|
|
(readtable:next potential-start
|
|
acc
|
|
port)))
|
|
(list readtable:update #\|
|
|
(lambda (this char acc port)
|
|
(readtable:next potential-end
|
|
acc
|
|
port))))))
|
|
loop))
|
|
|
|
(define read:datum-label
|
|
(lambda (location toplevel)
|
|
(let ((finalized? #f)
|
|
(value '())
|
|
(name (read:ident-builder location)))
|
|
(lambda (op . args)
|
|
(cond
|
|
((eq? op 'finalize-value)
|
|
(if finalized?
|
|
(error 'datum-label "cannot finalize twice"))
|
|
(set! finalized? #t)
|
|
(set! value (car args))
|
|
(set! toplevel #f))
|
|
((eq? op 'finalize->ident)
|
|
(set! name (name 'finalize->ident)))
|
|
((eq? op 'value)
|
|
(if (not finalized?)
|
|
(error 'datum-label "value called before finalize"))
|
|
value)
|
|
((eq? op 'toplevel) toplevel)
|
|
((eq? op 'type) 'datum-label)
|
|
((eq? op 'as-string) (name 'value))
|
|
(else (apply name op args)))))))
|
|
|
|
;;; Readtable for the number part of a datum label / reference. A label
|
|
;;; looks like "#[NUMBER]=" and a reference looks like "#[NUMBER]#".
|
|
;;;
|
|
;;; Datum label assignments #XXX=[DATUM] return DATUM.
|
|
;;; Datum label references #XXX# return a DATUM-LABEL object, because
|
|
;;; circular references must be resolved later. (With some trickery it
|
|
;;; cold be resolved as soon as possible, but that requires knowledge of
|
|
;;; what is complex data and what is an atom. This requires knowing all
|
|
;;; possible values that the toplevel could read, which is not possible
|
|
;;; because new items can be added to the toplevel.)
|
|
(define readtable:datum-label-next
|
|
(readtable:process
|
|
(readtable:empty/default (readtable:error 'datum-label-next
|
|
"invalid datum label/ref"))
|
|
(list readtable:update readtable:digits readtable:push-char)
|
|
(list readtable:update #\=
|
|
(lambda (_ __ acc port)
|
|
(acc 'finalize->ident)
|
|
(port 'set-datum-label! (acc 'as-string) acc)
|
|
(let ((next-value (readtable:next (acc 'toplevel)
|
|
#f
|
|
port)))
|
|
(if (eqv? acc next-value)
|
|
(error 'datum-label-next "datum label cannot be itself"))
|
|
(acc 'finalize-value next-value)
|
|
(acc 'value))))
|
|
(list readtable:update #\#
|
|
(lambda (_ __ acc port)
|
|
(acc 'finalize->ident)
|
|
(let ((datum-label-container (port 'get-datum-label
|
|
(acc 'as-string))))
|
|
(if (null? datum-label-container)
|
|
(error 'datum-label-next
|
|
"unknown reference to datum label" label)
|
|
(map:val datum-label-container)))))))
|
|
|
|
;;; Reads the next toplevel datum, discards it, and then continues at the
|
|
;;; toplevel.
|
|
;;;
|
|
;;; The R7RS reader can cause side-effects due to #!FOLD-CASE and datum
|
|
;;; labels. This must be supressed in datum comments.
|
|
(define readtable:datum-comment
|
|
(lambda (_ __ toplevel port)
|
|
(let ((mutable (port 'dump-mutable)))
|
|
(readtable:next toplevel #f port)
|
|
(port 'restore-mutable! mutable))
|
|
(readtable:next toplevel #f port)))
|
|
|
|
;;; ;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;;; Handling hash messages
|
|
;;;
|
|
;;; A "hash message" is any identifier that immediately follows a "#".
|
|
;;; This can be a constant, a part of a constant (like for numbers), or
|
|
;;; a directive (like #!FOLD-CASE).
|
|
|
|
;;; String map from constants to procedures with formal arguments
|
|
;;; (TOPLEVEL PORT)
|
|
;;; with TOPLEVEL being the current toplevel table and PORT being the
|
|
;;; current port being read from.
|
|
;;;
|
|
;;; Each one must return something. Directives that return nothing must
|
|
;;; call the toplevel again.
|
|
(define read:hash-messages
|
|
(smap:insert-many
|
|
'()
|
|
(cons "true" (lambda unused #t))
|
|
(cons "false" (lambda unused #f))
|
|
(cons "t" (lambda unused #t))
|
|
(cons "f" (lambda unused #f))
|
|
(cons "u8" (lambda (toplevel port)
|
|
(list 'bytevector
|
|
(readtable:expect-proper-list toplevel port))))
|
|
(cons "!fold-case"
|
|
(lambda (toplevel port)
|
|
(port 'fold-case! #t)
|
|
(readtable:act toplevel (port 'read) #f port)))
|
|
(cons "!no-fold-case"
|
|
(lambda (toplevel port)
|
|
(port 'fold-case! #f)
|
|
(readtable:act toplevel (port 'read) #f port)))))
|
|
|
|
(define read:read-hash-messages
|
|
(lambda (_ char acc port)
|
|
(let ((ident (readtable:read-ident #f char #f port)))
|
|
(let ((container (smap:search read:hash-messages
|
|
(ident 'value))))
|
|
(if (null? container)
|
|
(let ((number-port (ident->read (port 'location) ident)))
|
|
(number-port 'fold-case! #t)
|
|
(readtable:next readtable:read-prefix-char
|
|
(read:number-builder readtable:for-dec)
|
|
number-port))
|
|
((map:val container) acc port))))))
|
|
|
|
;;; ;;;;;;;;;;;;;;;;;;;;;;
|
|
;;; Characters
|
|
;;;
|
|
;;; For completeness, this adds a few more newline characters that are C
|
|
;;; escape sequences but are not standard Scheme.
|
|
|
|
(define read:named-characters
|
|
(smap:insert-many
|
|
'()
|
|
(cons "null" (integer->char 0))
|
|
(cons "alarm" (integer->char #x7))
|
|
(cons "backspace" (integer->char #x8))
|
|
(cons "tab" (integer->char #x9))
|
|
(cons "newline" (integer->char #xA))
|
|
(cons "vertical-tab" (integer->char #xB))
|
|
(cons "form-feed" (integer->char #xC))
|
|
(cons "return" (integer->char #xD))
|
|
(cons "escape" (integer->char #x1B))
|
|
(cons "space" (integer->char #x20))
|
|
(cons "delete" (integer->char #x7F))))
|
|
|
|
(define readtable:character
|
|
(lambda (_ char __ port)
|
|
(let ((char (port 'read)))
|
|
(let ((ident (readtable:read-ident #f char #f port)))
|
|
(let ((container (smap:search read:named-characters
|
|
(ident 'value))))
|
|
(display (ident 'value))
|
|
(newline)
|
|
(cond
|
|
((and (null? container)
|
|
(= (string-length (ident 'value)) 1))
|
|
(string-ref (ident 'value) 0))
|
|
((null? container) (error 'character 'unknown-character ident))
|
|
(else (map:val container))))))))
|
|
|
|
(define readtable:hash
|
|
(readtable:process
|
|
(readtable:empty/default read:read-hash-messages)
|
|
(list readtable:update readtable:ASCII-whitespace
|
|
(readtable:error 'hash 'whitespace-after-hash))
|
|
(list readtable:update #\| (readtable:jump/next readtable:block-comment))
|
|
(list readtable:update #\; readtable:datum-comment)
|
|
(list readtable:update #\\ readtable:character)
|
|
(list readtable:update readtable:digits ; Datum labels
|
|
(lambda (_ char toplevel port)
|
|
(readtable:act readtable:datum-label-next
|
|
char
|
|
(read:datum-label (port 'location) toplevel)
|
|
port)))
|
|
(list readtable:update %bol readtable:vector)))
|
|
|
|
;;; ;;;;;;;;;;;;;;;;
|
|
;;; Toplevel reader.
|
|
;;; ;;;;;;;;;;;;;;;;
|
|
;;; This is defined as a function so that it dynamically loads each
|
|
;;; sub-readtable.
|
|
(define readtable:top
|
|
(lambda ()
|
|
(readtable:process
|
|
(readtable:empty/default readtable:read-ident)
|
|
(list readtable:update readtable:ASCII-whitespace readtable:skip)
|
|
(list readtable:update #f (readtable:return 'eof))
|
|
(list readtable:update %bol readtable:read-list)
|
|
(list readtable:update %eol (readtable:error 'top "unbalanced list"))
|
|
(list readtable:update #\# (readtable:next/old-as-acc
|
|
readtable:hash))
|
|
(list readtable:update #\;
|
|
(readtable:jump-discard readtable:read-to-newline)))))
|
|
|
|
(define read/toplevel
|
|
(lambda (port)
|
|
;; Does each invocation of READ keep datum labels from previous reads?
|
|
;; (port 'clear-datum-labels!)
|
|
(readtable:next (readtable:top)
|
|
#f
|
|
port)))
|
|
|
|
(define intset:insert (set:insert (set:update integer<=>)))
|
|
(define intset:in (set:in integer<=>))
|
|
|
|
(define uncycle
|
|
(lambda (value)
|
|
(let ((cntr 0)
|
|
(used-counters '())
|
|
(pointers '()))
|
|
(letrec ((uncycle
|
|
(lambda (value)
|
|
(cond
|
|
((pair? value)
|
|
(let ((pair (assq value pointers)))
|
|
(if (pair? pair)
|
|
(begin
|
|
(set! used-counters
|
|
(car (intset:insert used-counters (cdr pair))))
|
|
(list 'ref (cdr pair)))
|
|
(begin
|
|
(set! pointers (cons (cons value cntr)
|
|
pointers))
|
|
(let ((cur-cntr cntr))
|
|
(set! cntr (+ 1 cntr))
|
|
(let ((returned (cons (uncycle (car value))
|
|
(uncycle (cdr value)))))
|
|
(if (not (null? (intset:in used-counters cur-cntr)))
|
|
(list 'def cur-cntr '= returned)
|
|
returned)))))))
|
|
((procedure? value)
|
|
(let ((type (value 'type)))
|
|
(cond
|
|
((eq? type 'ident) (value 'value))
|
|
((eq? type 'datum-label) (uncycle (value 'value)))
|
|
(else (vector 'unrepresentable type)))))
|
|
(else value)))))
|
|
(uncycle value)))))
|
|
|
|
;;; ;;;;;;;;;;;
|
|
;;; Test reader
|
|
;;; ;;;;;;;;;;;
|
|
(define %list->read
|
|
(lambda (seq)
|
|
(port->read
|
|
(lambda ()
|
|
(if (null? seq)
|
|
#f
|
|
(let ((ch (car seq)))
|
|
(set! seq (cdr seq))
|
|
ch)))
|
|
"test")))
|
|
|
|
(define read-all
|
|
(lambda (str)
|
|
(let ((reader (%list->read (string->list str))))
|
|
(letrec ((loop
|
|
(lambda ()
|
|
(if (not (reader 'peek))
|
|
#t
|
|
(let ((value (read/toplevel reader)))
|
|
(display (list "return" (uncycle value)))
|
|
(newline)
|
|
(loop))))))
|
|
(loop)))))
|
|
|
|
(read-all "x yy zz ; this is a comment\nx call/cc ")
|
|
(read-all "(a b c def (ghi j) k )")
|
|
(read-all "( a . b )")
|
|
(read-all "( a .b . c)")
|
|
(read-all "#( a b y)")
|
|
(read-all "(x y #| this is a block\n comment\n |# z w)")
|
|
(read-all "#( a b #| this is a #| nested block |# comment|# z w)")
|
|
(read-all "#(a b #(c #|close#|comment|#|#y))")
|
|
(read-all "(this has a #;(call with (current continuation)) datum comment)")
|
|
(read-all "#0=(#0# not unix)")
|
|
(read-all "#!no-fold-case #!fold-case #!NO-FOLD-CASE #false")
|
|
(read-all "#!fold-case #TRUE")
|
|
(read-all "#u8(x y z w)")
|
|
(read-all "#\\newline")
|
|
(read-all "#\\a")
|
|
|
|
(read-all "#b11")
|
|
(read-all "#XFF")
|
|
(read-all "#i#x10")
|
|
(read-all "#d1234.5678")
|
|
(read-all "#e10.5")
|
|
(read-all "#d10.24f12")
|