-;;;; peg.scm --- Parsing Expression Grammar (PEG) parser generator
-;;;;
-;;;; Copyright (C) 2010, 2011 Free Software Foundation, Inc.
-;;;;
-;;;; This library is free software; you can redistribute it and/or
-;;;; modify it under the terms of the GNU Lesser General Public
-;;;; License as published by the Free Software Foundation; either
-;;;; version 3 of the License, or (at your option) any later version.
-;;;;
-;;;; This library is distributed in the hope that it will be useful,
-;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
-;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-;;;; Lesser General Public License for more details.
-;;;;
-;;;; You should have received a copy of the GNU Lesser General Public
-;;;; License along with this library; if not, write to the Free Software
-;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
-;;;;
-
-(define-module (ice-9 peg)
- #:export (peg-parse
- define-nonterm
-; define-nonterm-f
- peg-match)
-; #:export-syntax (define-nonterm)
- #:use-module (ice-9 peg codegen)
- #:use-module (ice-9 peg string-peg)
- #:use-module (ice-9 peg simplify-tree)
- #:use-module (ice-9 peg match-record)
- #:re-export (peg-sexp-compile
- define-grammar
- define-grammar-f
-; define-nonterm
- keyword-flatten
- context-flatten
- peg:start
- peg:end
- peg:string
- peg:tree
- peg:substring
- peg-record?))
-
-;;;
-;;; Helper Macros
-;;;
-
-(define-syntax until
- (syntax-rules ()
- "Evaluate TEST. If it is true, return its value. Otherwise,
-execute the STMTs and try again."
- ((_ test stmt stmt* ...)
- (let lp ()
- (or test
- (begin stmt stmt* ... (lp)))))))
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;;;; FOR DEFINING AND USING NONTERMINALS
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
-;; Parses STRING using NONTERM
-(define (peg-parse nonterm string)
- ;; We copy the string before using it because it might have been modified
- ;; in-place since the last time it was parsed, which would invalidate the
- ;; cache. Guile uses copy-on-write for strings, so this is fast.
- (let ((res (nonterm (string-copy string) (string-length string) 0)))
- (if (not res)
- #f
- (make-prec 0 (car res) string (string-collapse (cadr res))))))
-
-;; The results of parsing using a nonterminal are cached. Think of it like a
-;; hash with no conflict resolution. Process for deciding on the cache size
-;; wasn't very scientific; just ran the benchmarks and stopped a little after
-;; the point of diminishing returns on my box.
-(define *cache-size* 512)
-
-;; Defines a new nonterminal symbol accumulating with ACCUM.
-(define-syntax define-nonterm
- (lambda (x)
- (syntax-case x ()
- ((_ sym accum pat)
- (let ((matchf (peg-sexp-compile #'pat (syntax->datum #'accum)))
- (accumsym (syntax->datum #'accum))
- (c (datum->syntax x (gensym))));; the cache
- ;; CODE is the code to parse the string if the result isn't cached.
- (let ((syn (wrap-parser-for-users x matchf accumsym #'sym)))
- #`(begin
- (define #,c (make-vector *cache-size* #f));; the cache
- (define (sym str strlen at)
- (let* ((vref (vector-ref #,c (modulo at *cache-size*))))
- ;; Check to see whether the value is cached.
- (if (and vref (eq? (car vref) str) (= (cadr vref) at))
- (caddr vref);; If it is return it.
- (let ((fres ;; Else calculate it and cache it.
- (#,syn str strlen at)))
- (vector-set! #,c (modulo at *cache-size*)
- (list str at fres))
- fres)))))))))))
-
-;; Searches through STRING for something that parses to PEG-MATCHER. Think
-;; regexp search.
-(define-syntax peg-match
- (lambda (x)
- (syntax-case x ()
- ((_ pattern string-uncopied)
- (let ((pmsym (syntax->datum #'pattern)))
- (let ((matcher (if (string? (syntax->datum #'pattern))
- (peg-string-compile #'pattern 'body)
- (peg-sexp-compile #'pattern 'body))))
- ;; We copy the string before using it because it might have been
- ;; modified in-place since the last time it was parsed, which would
- ;; invalidate the cache. Guile uses copy-on-write for strings, so
- ;; this is fast.
- #`(let ((string (string-copy string-uncopied))
- (strlen (string-length string-uncopied))
- (at 0))
- (let ((ret (until (or (>= at strlen)
- (#,matcher string strlen at))
- (set! at (+ at 1)))))
- (if (eq? ret #t) ;; (>= at strlen) succeeded
- #f
- (let ((end (car ret))
- (match (cadr ret)))
- (make-prec
- at end string
- (string-collapse match))))))))))))
+;;;; peg.scm --- Parsing Expression Grammar (PEG) parser generator
+;;;;
+;;;; Copyright (C) 2010, 2011 Free Software Foundation, Inc.
+;;;;
+;;;; This library is free software; you can redistribute it and/or
+;;;; modify it under the terms of the GNU Lesser General Public
+;;;; License as published by the Free Software Foundation; either
+;;;; version 3 of the License, or (at your option) any later version.
+;;;;
+;;;; This library is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;;;; Lesser General Public License for more details.
+;;;;
+;;;; You should have received a copy of the GNU Lesser General Public
+;;;; License along with this library; if not, write to the Free Software
+;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+;;;;
+
+(define-module (ice-9 peg)
+ #:use-module (ice-9 peg codegen)
+ #:use-module (ice-9 peg string-peg)
+ ;; Note: the most important effect of using string-peg is not whatever
+ ;; functions it exports, but the fact that it adds a new handler to
+ ;; peg-sexp-compile.
+ #:use-module (ice-9 peg simplify-tree)
+ #:use-module (ice-9 peg using-parsers)
+ #:use-module (ice-9 peg cache)
+ #:re-export (define-peg-pattern
+ define-peg-string-patterns
+ match-pattern
+ search-for-pattern
+ compile-peg-pattern
+ keyword-flatten
+ context-flatten
+ peg:start
+ peg:end
+ peg:string
+ peg:tree
+ peg:substring
+ peg-record?))
+
HCoop / bpt / guile.git / blobdiff