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Diffstat (limited to 'module/ice-9/peg/using-parsers.scm')
-rw-r--r-- | module/ice-9/peg/using-parsers.scm | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/module/ice-9/peg/using-parsers.scm b/module/ice-9/peg/using-parsers.scm new file mode 100644 index 000000000..076de2999 --- /dev/null +++ b/module/ice-9/peg/using-parsers.scm @@ -0,0 +1,116 @@ +;;;; using-parsers.scm --- utilities to make using parsers easier +;;;; +;;;; 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 using-parsers) + #:use-module (ice-9 peg simplify-tree) + #:use-module (ice-9 peg codegen) + #:use-module (ice-9 peg cache) + #:export (match-pattern define-peg-pattern search-for-pattern + prec make-prec 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 (match-pattern 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)))))) + +;; Defines a new nonterminal symbol accumulating with ACCUM. +(define-syntax define-peg-pattern + (lambda (x) + (syntax-case x () + ((_ sym accum pat) + (let ((matchf (compile-peg-pattern #'pat (syntax->datum #'accum))) + (accumsym (syntax->datum #'accum))) + ;; CODE is the code to parse the string if the result isn't cached. + (let ((syn (wrap-parser-for-users x matchf accumsym #'sym))) + #`(define sym #,(cg-cached-parser syn)))))))) + +(define (peg-like->peg pat) + (syntax-case pat () + (str (string? (syntax->datum #'str)) #'(peg str)) + (else pat))) + +;; Searches through STRING for something that parses to PEG-MATCHER. Think +;; regexp search. +(define-syntax search-for-pattern + (lambda (x) + (syntax-case x () + ((_ pattern string-uncopied) + (let ((pmsym (syntax->datum #'pattern))) + (let ((matcher (compile-peg-pattern (peg-like->peg #'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)))))))))))) + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;;;;; PMATCH STRUCTURE MUNGING +;; Pretty self-explanatory. +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + +(define prec + (make-record-type "peg" '(start end string tree))) +(define make-prec + (record-constructor prec '(start end string tree))) +(define (peg:start pm) + (if pm ((record-accessor prec 'start) pm) #f)) +(define (peg:end pm) + (if pm ((record-accessor prec 'end) pm) #f)) +(define (peg:string pm) + (if pm ((record-accessor prec 'string) pm) #f)) +(define (peg:tree pm) + (if pm ((record-accessor prec 'tree) pm) #f)) +(define (peg:substring pm) + (if pm (substring (peg:string pm) (peg:start pm) (peg:end pm)) #f)) +(define peg-record? (record-predicate prec)) |