readtables, first pass
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README.rst
20
README.rst
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@ -16,11 +16,23 @@ designed to be used by a severely limited Scheme interpreter, which
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* lacks ``call/cc``, ``call-with-values``, etc
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* lacks ``call/cc``, ``call-with-values``, etc
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* lacks user definable macros
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* lacks user definable macros
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* only uses required features from R3RS
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(except ``open-input-port``, ``close-input-port``, ``read-char``,
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``open-output-port``, ``close-output-port``, ``write-char``)
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* has fixnums only
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* has fixnums only
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* only uses immutable strings
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* only uses immutable strings
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* does not use "load" recursively
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* does not use "load" recursively
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* uses R3RS essental procedures only (with some exceptions)
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The goal is to have the compiler run under the MiniScheme in ``miniscm``
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in DOS, and then run in GLLV to compile itself.
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A proper implementation must have
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* ``open-input-port``, ``read-char``
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* ``open-output-port``, ``write-char``
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* ``cond-expand``
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* ``and``, ``or``
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* ``error``
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If your system supports any macro system at all, ``cond-expand``,
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``and``, and ``or`` can be implemented. ``error`` can be implemented
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as in SRFI-23 : https://srfi.schemers.org/srfi-23/srfi-23.html .
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The goal is to have the compiler run under MiniScheme in DOS.
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@ -47,3 +47,8 @@
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(begin evaluated ...)
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(begin evaluated ...)
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(cond-expand rest ...)))))
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(cond-expand rest ...)))))
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(define %r6rs-error error)
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(define (error . rest)
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(apply %r6rs-error (cons "UNSLISP" rest)))
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@ -0,0 +1,300 @@
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;;; 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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;;; The reader is based on a readtable that acts (in some instances) like
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;;; a trie. The reader reads a character and looks it up in the readtable.
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;;; The actions stored in the readtable are either opaque execution actions
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;;; or transparent "pass" actions that jump to a new readtable to read more
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;;; characters.
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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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;;; ;;;;;;;;;;;;;;;;;;;;;;;;
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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 port->read
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(lambda (read-function filename)
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(let ((line-number 1)
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(offset 0)
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(pushback-buffer '()))
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(let ((update-position
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(lambda (ch)
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(cond
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((or (eof-object? ch) (not ch)) (set! ch #f))
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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 (set! offset (+ 1 offset))))
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ch)))
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(lambda (op . args)
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(cond
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((eq? op 'pos) (list filename line-number offset))
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((eq? op 'read)
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(update-position
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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 '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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(else (error "read->port: invalid" args))))))))
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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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(define char<=>
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(lambda (x y)
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(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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(define charmap:insert-many
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(lambda (cmap . pairs)
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(fold (lambda (pair cmap)
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(car (charmap:insert cmap (car pair) (cdr pair))))
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cmap
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pairs)))
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;;; ;;;;;;;;;;
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;;; Readtable constructors
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;;;
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;;; Readtable actions are objects with the following messages:
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;;;
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;;; (STEP TABLE CHAR ACC PORT): Act on CHAR from TABLE with accumulated
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;;; value ACC and PORT.
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;;; (UPDATE REST ACTION): Return a new readtable action which is the
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;;; action of reading REST and executing ACTION after that. This should
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;;; preserve the previous action as much as possible.
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;;; ;;;;;;;;;;
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;;; Pass to new readtable.
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;;;
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;;; STEP reads the next character in the sequence and jumps to TABLE
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;;; modifying ACC.
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;;;
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;;; On UPDATE:
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;;; If (NULL? REST), return PASS with a TABLE updated with its default
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;;; action to be ACTION.
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;;; If (PAIR? REST), return PASS with (TABLE UPDATE REST ACTION).
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(define readtable:pass:new
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(lambda (table)
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(let ((step
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(lambda (oldtable char acc port)
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(table (port 'read) acc port)))
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(update
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(lambda (rest action)
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(readtable:pass:new
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(if (null? rest)
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(table 'with-default-action action)
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(table 'update rest action))))))
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(lambda (op . args)
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(cond
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((eq? op 'update) (apply update args))
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((eq? op 'step) (apply step args))
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(else (error "readtable:pass: invalid" args)))))))
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;;; Execute an action.
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;;;
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;;; STEP calls PROC with the same arguments.
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;;;
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;;; On UPDATE:
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;;; If (NULL? REST), then replace this action with ACTION.
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;;; If (PAIR? REST), return PASS with an empty table with this object
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;;; as the default action, and run (UPDATE REST ACTION) on it.
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(define readtable:exec:new
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(lambda (proc)
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(let ((update
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(lambda (rest action)
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(if (null? rest)
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action
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((readtable:pass:new readtable:empty)
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'update rest action)))))
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(lambda (op . args)
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(cond
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((eq? op 'update) (apply update args))
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((eq? op 'step) (apply proc args))
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(else (error "readtable:exec: invalid" args)))))))
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;;; Define a new readtable.
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;;;
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;;; (X) where (CHAR? X): Execute the action associated with X, or the
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;;; default action.
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;;;
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;;; (WITH-DEFAULT-ACTION NEW-ACTION): Return a readtable with the same
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;;; backing table but with NEW-ACTION as the default action.
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;;;
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;;; (UPDATE REST ACTION): Update the action taken by the total application
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;;; of REST to be ACTION. REST must be a pair.
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(define readtable:new
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(lambda (default-action charmap)
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(letrec
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((lookup?
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(lambda (char)
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(let ((node (charmap:search charmap char)))
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(if (null? node)
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#f
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(map:val node)))))
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(lookup
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(lambda (char)
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(or (lookup? char) default-action)))
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(run*
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(lambda (handler char acc port)
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(handler 'step table char acc port)))
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(run
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(lambda (char acc port)
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(run* (lookup char) char acc port)))
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(with-default-action
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(lambda (new-default-action)
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(readtable:new new-default-action charmap)))
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(update
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(lambda (rest action)
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(if (null? rest)
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(error "readtable update: invalid" (list rest action))
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(readtable:new default-action
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(charmap:update
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charmap
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(car rest)
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(lambda (_ oldnode)
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(if (null? oldnode)
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(action 'update (cdr rest) action)
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((map:val oldnode)
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'update (cdr rest) action))))))))
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(table
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(lambda (op . args)
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(cond
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((not op)
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(display (list op args))
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(apply run* default-action op args))
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((char? op) (apply run op args))
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((eq? op 'with-default-action) (apply with-default-action
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args))
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((eq? op 'update) (apply update args))
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(else (error "readtable: invalid" args))))))
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table)))
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;;; Add ACTION as the action to be taken in TABLE following SEQ.
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(define readtable:add-sequence
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(lambda (table seq action)
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(let ((seq (cond
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((char? seq) (list seq))
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((string? seq) (string->list seq))
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(else seq))))
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(table 'update seq action))))
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;;; ;;;;;;;;;;;;;;;
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;;; Default actions
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;;; ;;;;;;;;;;;;;;;
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(define readtable:update-many
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(lambda (table . pairs)
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(fold (lambda (pair table)
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(readtable:add-sequence table (car pair)
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(cdr pair)))
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table
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pairs)))
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;;; Signal error on this action.
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(define readtable:error-action
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(lambda (emsg)
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(readtable:exec:new
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(lambda (table char acc port)
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(error emsg (list table char acc port))))))
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;;; Create an EXEC action that discards the current character.
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;;; This should not be a PASS action, because PASS actions emulate
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;;; a trie, which is not cyclic.
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(define readtable:skip
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(readtable:exec:new
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(lambda (table char acc port)
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(table 'run (port 'read) acc port))))
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;;; Ignore everything and return a constant.
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(define readtable:return-value
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(lambda (value)
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(readtable:exec:new
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(lambda (table char acc port)
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value))))
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;;; ;;;;;;;;;;;;;;;;;;;
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;;; Default readtables
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;;; ;;;;;;;;;;;;;;;;;;;
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(define readtable:empty
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(readtable:new (readtable:error-action "no more actions")
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'()))
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;;; Ignore all characters until newline.
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(define readtable:read-line-comment
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(readtable:new
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readtable:skip
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(charmap:insert-many '()
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(list
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(cons #\newline (readtable:return-value #f))))))
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(define readtable:top
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(readtable:update-many
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readtable:empty
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(cons "#t" (readtable:return-value #t))
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(cons "#f" (readtable:return-value #f))
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(cons "#true" (readtable:return-value #t))))
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;;; ;;;;;;;;;;;
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;;; Test reader
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;;; ;;;;;;;;;;;
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(define %list->read
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(lambda (seq)
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(port->read
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(lambda ()
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(if (null? seq)
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#f
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(let ((ch (car seq)))
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(set! seq (cdr seq))
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ch)))
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"test")))
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(let ((true-reader (%list->read (list #\# #\t))))
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(readtable:top (true-reader 'read) #f true-reader))
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@ -69,8 +69,3 @@
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(display "running string BST-AVL tests")
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(display "running string BST-AVL tests")
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(newline)
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(newline)
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(report-tests %set:tests)
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(report-tests %set:tests)
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(load "trie.scm")
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(display "char trie")
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(newline)
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(report-tests %trie:tests)
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138
trie.scm
138
trie.scm
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@ -1,138 +0,0 @@
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;;; 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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;;; ;;;;;;;;;;;;;;
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;;; Character maps
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;;; ;;;;;;;;;;;;;;
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(define char<=>
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(lambda (x y)
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(let ((x (char->integer x))
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(y (char->integer 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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(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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;;; Char tries
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;;;
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;;; Tries are pairs, CAR = backing map from chars to trie nodes, and
|
|
||||||
;;; CDR = function tied to this part of the trie.
|
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||||||
;;; ;;;;;;;;;;
|
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||||||
|
|
||||||
;;; (TRIE:NEW TABLE FUNCTION)
|
|
||||||
(define trie:new cons)
|
|
||||||
(define trie:empty (trie:new '() #f))
|
|
||||||
|
|
||||||
;;; Get the function inside of trie NODE.
|
|
||||||
(define trie:function
|
|
||||||
(lambda (node)
|
|
||||||
(if (null? node)
|
|
||||||
#f
|
|
||||||
(cdr node))))
|
|
||||||
|
|
||||||
;;; Get the backing set inside of trie NODE.
|
|
||||||
(define trie:backing
|
|
||||||
(lambda (node)
|
|
||||||
(if (null? node)
|
|
||||||
'()
|
|
||||||
(car node))))
|
|
||||||
|
|
||||||
;;; Insert STRING-AS-LIST into NODE with value FUNCTION.
|
|
||||||
(define trie:insert
|
|
||||||
(lambda (node string-as-list function)
|
|
||||||
(if (null? string-as-list)
|
|
||||||
(trie:new (trie:backing node) function)
|
|
||||||
(let ((ch (car string-as-list))
|
|
||||||
(string-as-list (cdr string-as-list)))
|
|
||||||
(let ((newtree (charmap:update (trie:backing node) ch
|
|
||||||
(lambda (node oldnode)
|
|
||||||
(if oldnode
|
|
||||||
(map:node-new-val
|
|
||||||
oldnode
|
|
||||||
ch
|
|
||||||
(trie:insert (map:val oldnode)
|
|
||||||
string-as-list
|
|
||||||
function))
|
|
||||||
(map:empty-node ch
|
|
||||||
(trie:insert
|
|
||||||
trie:empty
|
|
||||||
string-as-list
|
|
||||||
function)))))))
|
|
||||||
(trie:new newtree (trie:function node)))))))
|
|
||||||
|
|
||||||
(define trie:insert-many
|
|
||||||
(lambda (node lst)
|
|
||||||
(fold (lambda (pair node)
|
|
||||||
(let ((key (car pair)))
|
|
||||||
(let ((key (cond
|
|
||||||
((list? key) key)
|
|
||||||
((string? key) (string->list key))
|
|
||||||
((char? key) (list key)))))
|
|
||||||
(trie:insert node key (cdr pair)))))
|
|
||||||
node lst)))
|
|
||||||
|
|
||||||
;;; Search for CH in NODE.
|
|
||||||
(define trie:search-single
|
|
||||||
(lambda (ch node)
|
|
||||||
(if (null? node)
|
|
||||||
'()
|
|
||||||
(let ((node (charmap:search (trie:backing node) ch)))
|
|
||||||
(if (null? node)
|
|
||||||
'()
|
|
||||||
(map:val node))))))
|
|
||||||
|
|
||||||
(define trie:search
|
|
||||||
(lambda (node str)
|
|
||||||
(fold trie:search-single node (string->list str))))
|
|
||||||
|
|
||||||
;;; ;;;;;
|
|
||||||
;;; Tests
|
|
||||||
;;; ;;;;;
|
|
||||||
|
|
||||||
(define %trie:tests
|
|
||||||
(list
|
|
||||||
(cons "insert with prefixes"
|
|
||||||
(lambda ()
|
|
||||||
(let ((trie
|
|
||||||
(trie:insert-many trie:empty
|
|
||||||
(list
|
|
||||||
(cons (string #\a #\b #\c #\d) 10)
|
|
||||||
(cons (string #\a #\b #\c) 20)
|
|
||||||
(cons (string #\a #\b #\c #\d #\e) 30)
|
|
||||||
(cons (string #\b) 40)
|
|
||||||
(cons (string #\b #\e #\g) 50))))
|
|
||||||
(t '()))
|
|
||||||
(set! t (trie:search trie (string #\a #\b #\c)))
|
|
||||||
(if (not (= (trie:function t) 20))
|
|
||||||
"abc not found"
|
|
||||||
(let ((t (trie:search-single #\d t)))
|
|
||||||
(if (not (= (trie:function t) 10))
|
|
||||||
"abcd not found"
|
|
||||||
(let ((t (trie:search-single #\e t)))
|
|
||||||
(if (not (= (trie:function t) 30))
|
|
||||||
"abcde not found"
|
|
||||||
(let ((t (trie:search-single #\b trie)))
|
|
||||||
(if (not (= (trie:function t) 40))
|
|
||||||
"b not found"
|
|
||||||
(let ((t (trie:search t (string #\e #\g))))
|
|
||||||
(= (trie:function t) 50))))))))))))))
|
|
||||||
Loading…
Reference in New Issue