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;;;; Copyright (C) 1997, 1999, 2001, 2004, 2005, 2006, 2008, 2010 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
;;;;
;;; Commentary:
;; These procedures are exported:
;; (match:count match)
;; (match:string match)
;; (match:prefix match)
;; (match:suffix match)
;; (regexp-match? match)
;; (regexp-quote string)
;; (match:start match . submatch-num)
;; (match:end match . submatch-num)
;; (match:substring match . submatch-num)
;; (string-match pattern str . start)
;; (regexp-substitute port match . items)
;; (fold-matches regexp string init proc . flags)
;; (list-matches regexp string . flags)
;; (regexp-substitute/global port regexp string . items)
;;; Code:
;;;; POSIX regex support functions.
(define-module (ice-9 regex)
#:export (match:count match:string match:prefix match:suffix
regexp-match? regexp-quote match:start match:end match:substring
string-match regexp-substitute fold-matches list-matches
regexp-substitute/global))
;; References:
;;
;; POSIX spec:
;; http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html
;;; FIXME:
;;; It is not clear what should happen if a `match' function
;;; is passed a `match number' which is out of bounds for the
;;; regexp match: return #f, or throw an error? These routines
;;; throw an out-of-range error.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;; These procedures are not defined in SCSH, but I found them useful.
(define (match:count match)
(- (vector-length match) 1))
(define (match:string match)
(vector-ref match 0))
(define (match:prefix match)
(substring (match:string match) 0 (match:start match 0)))
(define (match:suffix match)
(substring (match:string match) (match:end match 0)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;; SCSH compatibility routines.
(define (regexp-match? match)
(and (vector? match)
(string? (vector-ref match 0))
(let loop ((i 1))
(cond ((>= i (vector-length match)) #t)
((and (pair? (vector-ref match i))
(integer? (car (vector-ref match i)))
(integer? (cdr (vector-ref match i))))
(loop (+ 1 i)))
(else #f)))))
;; * . \ ^ $ and [ are special in both regexp/basic and regexp/extended and
;; can be backslash escaped.
;;
;; ( ) + ? { } and | are special in regexp/extended so must be quoted. But
;; that can't be done with a backslash since in regexp/basic where they're
;; not special, adding a backslash makes them become special. Character
;; class forms [(] etc are used instead.
;;
;; ) is not special when not preceded by a (, and * and ? are not special at
;; the start of a string, but we quote all of these always, so the result
;; can be concatenated or merged into some larger regexp.
;;
;; ] is not special outside a [ ] character class, so doesn't need to be
;; quoted.
;;
(define (regexp-quote string)
(call-with-output-string
(lambda (p)
(string-for-each (lambda (c)
(case c
((#\* #\. #\\ #\^ #\$ #\[)
(write-char #\\ p)
(write-char c p))
((#\( #\) #\+ #\? #\{ #\} #\|)
(write-char #\[ p)
(write-char c p)
(write-char #\] p))
(else
(write-char c p))))
string))))
(define* (match:start match #:optional (n 0))
(let ((start (car (vector-ref match (1+ n)))))
(if (= start -1) #f start)))
(define* (match:end match #:optional (n 0))
(let* ((end (cdr (vector-ref match (1+ n)))))
(if (= end -1) #f end)))
(define* (match:substring match #:optional (n 0))
(let* ((start (match:start match n))
(end (match:end match n)))
(and start end (substring (match:string match) start end))))
(define (string-match pattern str . args)
(let ((rx (make-regexp pattern))
(start (if (pair? args) (car args) 0)))
(regexp-exec rx str start)))
(define (regexp-substitute port match . items)
;; If `port' is #f, send output to a string.
(if (not port)
(call-with-output-string
(lambda (p)
(apply regexp-substitute p match items)))
;; Otherwise, process each substitution argument in `items'.
(for-each (lambda (obj)
(cond ((string? obj) (display obj port))
((integer? obj) (display (match:substring match obj) port))
((eq? 'pre obj) (display (match:prefix match) port))
((eq? 'post obj) (display (match:suffix match) port))
(else (error 'wrong-type-arg obj))))
items)))
;;; If we call fold-matches, below, with a regexp that can match the
;;; empty string, it's not obvious what "all the matches" means. How
;;; many empty strings are there in the string "a"? Our answer:
;;;
;;; This function applies PROC to every non-overlapping, maximal
;;; match of REGEXP in STRING.
;;;
;;; "non-overlapping": There are two non-overlapping matches of "" in
;;; "a" --- one before the `a', and one after. There are three
;;; non-overlapping matches of "q|x*" in "aqb": the empty strings
;;; before `a' and after `b', and `q'. The two empty strings before
;;; and after `q' don't count, because they overlap with the match of
;;; "q".
;;;
;;; "maximal": There are three distinct maximal matches of "x*" in
;;; "axxxb": one before the `a', one covering `xxx', and one after the
;;; `b'. Around or within `xxx', only the match covering all three
;;; x's counts, because the rest are not maximal.
(define* (fold-matches regexp string init proc #:optional (flags 0))
(let ((regexp (if (regexp? regexp) regexp (make-regexp regexp))))
(let loop ((start 0)
(value init)
(abuts #f)) ; True if start abuts a previous match.
(define bol (if (zero? start) 0 regexp/notbol))
(let ((m (if (> start (string-length string)) #f
(regexp-exec regexp string start (logior flags bol)))))
(cond
((not m) value)
((and (= (match:start m) (match:end m)) abuts)
;; We matched an empty string, but that would overlap the
;; match immediately before. Try again at a position
;; further to the right.
(loop (+ start 1) value #f))
(else
(loop (match:end m) (proc m value) #t)))))))
(define* (list-matches regexp string #:optional (flags 0))
(reverse! (fold-matches regexp string '() cons flags)))
(define (regexp-substitute/global port regexp string . items)
;; If `port' is #f, send output to a string.
(if (not port)
(call-with-output-string
(lambda (p)
(apply regexp-substitute/global p regexp string items)))
;; Walk the set of non-overlapping, maximal matches.
(let next-match ((matches (list-matches regexp string))
(start 0))
(if (null? matches)
(display (substring string start) port)
(let ((m (car matches)))
;; Process all of the items for this match. Don't use
;; for-each, because we need to make sure 'post at the
;; end of the item list is a tail call.
(let next-item ((items items))
(define (do-item item)
(cond
((string? item) (display item port))
((integer? item) (display (match:substring m item) port))
((procedure? item) (display (item m) port))
((eq? item 'pre)
(display
(substring string start (match:start m))
port))
((eq? item 'post)
(next-match (cdr matches) (match:end m)))
(else (error 'wrong-type-arg item))))
(if (pair? items)
(if (null? (cdr items))
(do-item (car items)) ; This is a tail call.
(begin
(do-item (car items)) ; This is not.
(next-item (cdr items)))))))))))
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