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; SILex - Scheme Implementation of Lex
; Copyright (C) 2001 Danny Dube'
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation; either version 2
; of the License, or (at your option) any later version.
;
; This program 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 General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
; Fonction "merge" qui elimine les repetitions
(define noeps-merge-1
(lambda (l1 l2)
(cond ((null? l1)
l2)
((null? l2)
l1)
(else
(let ((t1 (car l1))
(t2 (car l2)))
(cond ((< t1 t2)
(cons t1 (noeps-merge-1 (cdr l1) l2)))
((= t1 t2)
(cons t1 (noeps-merge-1 (cdr l1) (cdr l2))))
(else
(cons t2 (noeps-merge-1 l1 (cdr l2))))))))))
; Fabrication des voisinages externes
(define noeps-mkvois
(lambda (trans-v)
(let* ((nbnodes (vector-length trans-v))
(arcs (make-vector nbnodes '())))
(let loop1 ((n 0))
(if (< n nbnodes)
(begin
(let loop2 ((trans (vector-ref trans-v n)) (ends '()))
(if (null? trans)
(vector-set! arcs n ends)
(let* ((tran (car trans))
(class (car tran))
(end (cdr tran)))
(loop2 (cdr trans) (if (eq? class 'eps)
(noeps-merge-1 ends (list end))
ends)))))
(loop1 (+ n 1)))))
arcs)))
; Fabrication des valeurs initiales
(define noeps-mkinit
(lambda (trans-v)
(let* ((nbnodes (vector-length trans-v))
(init (make-vector nbnodes)))
(let loop ((n 0))
(if (< n nbnodes)
(begin
(vector-set! init n (list n))
(loop (+ n 1)))))
init)))
; Traduction d'une liste d'arcs
(define noeps-trad-arcs
(lambda (trans dict)
(let loop ((trans trans))
(if (null? trans)
'()
(let* ((tran (car trans))
(class (car tran))
(end (cdr tran)))
(if (eq? class 'eps)
(loop (cdr trans))
(let* ((new-end (vector-ref dict end))
(new-tran (cons class new-end)))
(cons new-tran (loop (cdr trans))))))))))
; Elimination des transitions eps
(define noeps
(lambda (nl-start no-nl-start arcs acc)
(let* ((digraph-arcs (noeps-mkvois arcs))
(digraph-init (noeps-mkinit arcs))
(dict (digraph digraph-arcs digraph-init noeps-merge-1))
(new-nl-start (vector-ref dict nl-start))
(new-no-nl-start (vector-ref dict no-nl-start)))
(let loop ((i (- (vector-length arcs) 1)))
(if (>= i 0)
(begin
(vector-set! arcs i (noeps-trad-arcs (vector-ref arcs i) dict))
(loop (- i 1)))))
(list new-nl-start new-no-nl-start arcs acc))))
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