readtable: add lists
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@ -19,7 +19,7 @@ designed to be used by a severely limited Scheme interpreter, which
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* has fixnums only
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* only uses immutable strings
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* does not use "load" recursively
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* uses R3RS essential procedures only (with some exceptions)
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* uses R3RS essential procedures/syntax 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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101
read.scm
101
read.scm
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@ -17,6 +17,7 @@
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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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;;; ;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Port reader wrapper
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@ -159,6 +160,12 @@
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;;; Default readtables
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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 tablemsg
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(apply error tablemsg emsg))))
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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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@ -178,6 +185,12 @@
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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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;;; Push back CHAR and return ACC.
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(define readtable:return-acc-keep-char
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(lambda (table char acc port)
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@ -185,9 +198,10 @@
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acc))
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;;; Push CHAR to ACC and continue reading from TABLE.
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(define readtable:push-acc
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(define readtable:push-char
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(lambda (table char acc port)
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(readtable:act table (port 'read) (cons 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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@ -210,7 +224,7 @@
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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-acc)
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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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@ -219,8 +233,12 @@
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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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(reverse (readtable:act readtable:identifier
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(port 'read) (list char) port))))
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(let ((lst (linked-list:new)))
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(lst 'push char)
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(list->string
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((readtable:act readtable:identifier
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(port 'read) lst port)
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'to-list)))))
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;;; Add all chars in TO-SKIP to TABLE as skipped characters. Used for
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;;; whitespace.
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@ -237,14 +255,69 @@
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(readtable:empty/default readtable:skip)
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(list readtable:update #\newline (readtable:return #f))))
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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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;;; TODO: Put improper list into new function
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(define readtable:read-list
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(lambda (table char acc port)
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(let ((acc (linked-list:new))
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(table (readtable:process
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table
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(list readtable:update #\)
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(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 ((id (readtable:read-ident
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table
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char
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acc
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port)))
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(if (equal? id ".")
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'period
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id)))))))
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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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#f
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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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((eqv? value 'period)
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(let ((final-value (readtable:act table
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(port 'read)
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#f
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port)))
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(acc 'set-cdr! final-value)
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(let ((expect-eol (readtable:act table
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(port 'read)
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#f
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port)))
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(if (not (eqv? expect-eol 'end-of-list))
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(error "found instead of end of improper list"
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expect-eol)
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(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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;;; Toplevel reader.
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;;; This is defined as a function so that it dynamically loads each
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;;; sub-readtable.
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(define readtable:top
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(readtable:process
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(readtable:empty/default readtable:read-ident)
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(list readtable:add-all-as-skip readtable:ASCII-whitespace)
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(list readtable:update #f (readtable:return 'eof))
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(list readtable:update #\;
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(readtable:jump-discard readtable:read-to-newline))))
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(lambda ()
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(readtable:process
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(readtable:empty/default readtable:read-ident)
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(list readtable:add-all-as-skip readtable:ASCII-whitespace)
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(list readtable:update #f (readtable:return 'eof))
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(list readtable:update #\( readtable:read-list)
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(list readtable:update #\) (readtable:error "unbalanced list"))
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(list readtable:update #\;
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(readtable:jump-discard readtable:read-to-newline)))))
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;;; ;;;;;;;;;;;
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;;; Test reader
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@ -268,7 +341,7 @@
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(if (not (reader 'peek))
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#t
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(let ((value (readtable:act
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readtable:top (reader 'read)
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(readtable:top) (reader 'read)
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#f
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reader)))
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(display (list "return" value))
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@ -277,5 +350,5 @@
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(loop)))))
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(read-all "x yy zz ; this is a comment\nx call/cc ")
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(read-all "(a b c def (ghi j) k )")
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(read-all "(a . b)")
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