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;; Packrat Parser Library
;;
;; Copyright (c) 2004, 2005 Tony Garnock-Jones <tonyg@kcbbs.gen.nz>
;; Copyright (c) 2005 LShift Ltd. <query@lshift.net>
;;
;; Permission is hereby granted, free of charge, to any person
;; obtaining a copy of this software and associated documentation
;; files (the "Software"), to deal in the Software without
;; restriction, including without limitation the rights to use, copy,
;; modify, merge, publish, distribute, sublicense, and/or sell copies
;; of the Software, and to permit persons to whom the Software is
;; furnished to do so, subject to the following conditions:
;;
;; The above copyright notice and this permission notice shall be
;; included in all copies or substantial portions of the Software.
;;
;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
;; EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
;; MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
;; NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
;; BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
;; ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
;; CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
;; SOFTWARE.
;; Requires: SRFI-1, SRFI-9, SRFI-6. See the documentation for more
;; details.
(require-extension (srfi 1 6 9))
(define-record-type parse-result
(make-parse-result successful? semantic-value next error)
parse-result?
(successful? parse-result-successful?)
(semantic-value parse-result-semantic-value)
(next parse-result-next) ;; #f, if eof or error; otherwise a parse-results
(error parse-result-error)
;; ^^ #f if none, but usually a parse-error structure
)
(define-record-type parse-results
(make-parse-results position base next map)
parse-results?
(position parse-results-position) ;; a parse-position or #f if unknown
(base parse-results-base) ;; a value, #f indicating 'none' or 'eof'
(next parse-results-next* set-parse-results-next!)
;; ^^ a parse-results, or a nullary function delivering same, or #f for nothing next (eof)
(map parse-results-map set-parse-results-map!)
;; ^^ an alist mapping a nonterminal to a parse-result
)
(define-record-type parse-error
(make-parse-error position expected messages)
parse-error?
(position parse-error-position) ;; a parse-position or #f if unknown
(expected parse-error-expected) ;; set of things (lset)
(messages parse-error-messages) ;; list of strings
)
(define-record-type parse-position
(make-parse-position file line column)
parse-position?
(file parse-position-file)
(line parse-position-line)
(column parse-position-column))
(define (top-parse-position filename)
(make-parse-position filename 1 0))
(define (update-parse-position pos ch)
(if (not pos)
#f
(let ((file (parse-position-file pos))
(line (parse-position-line pos))
(column (parse-position-column pos)))
(case ch
((#\return) (make-parse-position file line 0))
((#\newline) (make-parse-position file (+ line 1) 0))
((#\tab) (make-parse-position file line (* (quotient (+ column 8) 8) 8)))
(else (make-parse-position file line (+ column 1)))))))
(define (parse-position->string pos)
(if (not pos)
"<??>"
(string-append (parse-position-file pos) ":"
(number->string (parse-position-line pos)) ":"
(number->string (parse-position-column pos)))))
(define (empty-results pos)
(make-parse-results pos #f #f '()))
(define (make-results pos base next-generator)
(make-parse-results pos base next-generator '()))
(define (make-error-expected pos str)
(make-parse-error pos (list str) '()))
(define (make-error-message pos msg)
(make-parse-error pos '() (list msg)))
(define (make-result semantic-value next)
(make-parse-result #t semantic-value next #f))
(define (make-expected-result pos str)
(make-parse-result #f #f #f (make-error-expected pos str)))
(define (make-message-result pos msg)
(make-parse-result #f #f #f (make-error-message pos msg)))
(define (prepend-base pos base next)
(make-parse-results pos base next '()))
(define (prepend-semantic-value pos key result next)
(make-parse-results pos #f #f
(list (cons key (make-result result next)))))
(define (base-generator->results generator)
;; Note: applies first next-generator, to get first result
(define (results-generator)
(receive (pos base)
(generator)
(if (not base)
(empty-results pos)
(make-results pos base results-generator))))
(results-generator))
(define (parse-results-next results)
(let ((next (parse-results-next* results)))
(if (procedure? next)
(let ((next-value (next)))
(set-parse-results-next! results next-value)
next-value)
next)))
(define (results->result results key fn)
(let ((results-map (parse-results-map results)))
(cond
((assv key results-map) => cdr)
(else (let ((result (fn)))
(set-parse-results-map! results (cons (cons key result) results-map))
result)))))
(define (parse-position>? a b)
(cond
((not a) #f)
((not b) #t)
(else (let ((la (parse-position-line a)) (lb (parse-position-line b)))
(or (> la lb)
(and (= la lb)
(> (parse-position-column a) (parse-position-column b))))))))
(define (parse-error-empty? e)
(and (null? (parse-error-expected e))
(null? (parse-error-messages e))))
(define (merge-parse-errors e1 e2)
(cond
((not e1) e2)
((not e2) e1)
(else
(let ((p1 (parse-error-position e1))
(p2 (parse-error-position e2)))
(cond
((or (parse-position>? p1 p2) (parse-error-empty? e2)) e1)
((or (parse-position>? p2 p1) (parse-error-empty? e1)) e2)
(else (make-parse-error p1
(lset-union equal?
(parse-error-expected e1)
(parse-error-expected e2))
(append (parse-error-messages e1) (parse-error-messages e2)))))))))
(define (merge-result-errors result errs)
(make-parse-result (parse-result-successful? result)
(parse-result-semantic-value result)
(parse-result-next result)
(merge-parse-errors (parse-result-error result) errs)))
;---------------------------------------------------------------------------
(define (parse-results-token-kind results)
(let ((base (parse-results-base results)))
(and base (car base))))
(define (parse-results-token-value results)
(let ((base (parse-results-base results)))
(and base (cdr base))))
(define (packrat-check-base token-kind k)
(lambda (results)
(let ((base (parse-results-base results)))
(if (eqv? (and base (car base)) token-kind)
((k (and base (cdr base))) (parse-results-next results))
(make-expected-result (parse-results-position results)
(if (not token-kind)
"end-of-file"
token-kind))))))
(define (packrat-check parser k)
(lambda (results)
(let ((result (parser results)))
(if (parse-result-successful? result)
(merge-result-errors ((k (parse-result-semantic-value result))
(parse-result-next result))
(parse-result-error result))
result))))
(define (packrat-or p1 p2)
(lambda (results)
(let ((result (p1 results)))
(if (parse-result-successful? result)
result
(merge-result-errors (p2 results)
(parse-result-error result))))))
(define (packrat-unless explanation p1 p2)
(lambda (results)
(let ((result (p1 results)))
(if (parse-result-successful? result)
(make-message-result (parse-results-position results)
explanation)
(p2 results)))))
;---------------------------------------------------------------------------
(define (object->external-representation o)
(let ((s (open-output-string)))
(write o s)
(get-output-string s)))
(define-syntax packrat-parser
(syntax-rules (<- quote ! @ /)
((_ start (nonterminal (alternative body0 body ...) ...) ...)
(let ()
(define nonterminal
(lambda (results)
(results->result results 'nonterminal
(lambda ()
((packrat-parser #f "alts" nonterminal
((begin body0 body ...) alternative) ...)
results)))))
...
start))
((_ #f "alts" nt (body alternative))
(packrat-parser #f "alt" nt body alternative))
((_ #f "alts" nt (body alternative) rest0 rest ...)
(packrat-or (packrat-parser #f "alt" nt body alternative)
(packrat-parser #f "alts" nt rest0 rest ...)))
((_ #f "alt" nt body ())
(lambda (results) (make-result body results)))
((_ #f "alt" nt body ((! fails ...) rest ...))
(packrat-unless (string-append "Nonterminal " (symbol->string 'nt)
" expected to fail "
(object->external-representation '(fails ...)))
(packrat-parser #f "alt" nt #t (fails ...))
(packrat-parser #f "alt" nt body (rest ...))))
((_ #f "alt" nt body ((/ alternative ...) rest ...))
(packrat-check (packrat-parser #f "alts" nt (#t alternative) ...)
(lambda (result) (packrat-parser #f "alt" nt body (rest ...)))))
((_ #f "alt" nt body (var <- 'val rest ...))
(packrat-check-base 'val
(lambda (var)
(packrat-parser #f "alt" nt body (rest ...)))))
((_ #f "alt" nt body (var <- @ rest ...))
(lambda (results)
(let ((var (parse-results-position results)))
((packrat-parser #f "alt" nt body (rest ...)) results))))
((_ #f "alt" nt body (var <- val rest ...))
(packrat-check val
(lambda (var)
(packrat-parser #f "alt" nt body (rest ...)))))
((_ #f "alt" nt body ('val rest ...))
(packrat-check-base 'val
(lambda (dummy)
(packrat-parser #f "alt" nt body (rest ...)))))
((_ #f "alt" nt body (val rest ...))
(packrat-check val
(lambda (dummy)
(packrat-parser #f "alt" nt body (rest ...)))))))
'(define (x)
(sc-expand
'(packrat-parser expr
(expr ((a <- mulexp '+ b <- mulexp)
(+ a b))
((a <- mulexp) a))
(mulexp ((a <- simple '* b <- simple)
(* a b))
((a <- simple) a))
(simple ((a <- 'num) a)
(('oparen a <- expr 'cparen) a)))))
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