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{
DFA table construction. This code, admittedly, is not the most aesthetic,
but it's quite efficient (and that's the main goal). For further
explanation, refer to Aho/Sethi/Ullman 1986, Section 3.9.
Copyright (c) 1990-92 Albert Graef <ag@muwiinfa.geschichte.uni-mainz.de>
Copyright (C) 1996 Berend de Boer <berend@pobox.com>
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., 675 Mass Ave, Cambridge, MA 02139, USA.
$Revision: 1.2 $
$Modtime: 96-08-01 6:13 $
$History: LEXDFA.PAS $
*
* ***************** Version 2 *****************
* User: Berend Date: 96-10-10 Time: 21:16
* Updated in $/Lex and Yacc/tply
* Updated for protected mode, windows and Delphi 1.X and 2.X.
}
unit LexDFA;
interface
procedure makeDFATable;
(* construct DFA from position table *)
implementation
uses LexBase, LexTable;
procedure makeDFATable;
var i : Integer;
begin
(* initialize start states: *)
for i := 2 to 2*n_start_states+1 do
setunion(first_pos_table^[i]^, first_pos_table^[i mod 2]^);
for i := 0 to 2*n_start_states+1 do
act_state := newState(first_pos_table^[i]);
act_state := -1;
while succ(act_state)<n_states do
begin
inc(act_state);
(* add transitions for active state: *)
startStateTrans;
for i := 1 to size(state_table^[act_state].state_pos^) do
with pos_table^[state_table^[act_state].state_pos^[i]] do
if pos_type=char_pos then
addTrans([c], follow_pos)
else if pos_type=cclass_pos then
addTrans(cc^, follow_pos)
else if pos=0 then
state_table^[act_state].final := true;
(* assign next states: *)
for i := state_table^[act_state].trans_lo to n_trans do
with trans_table^[i] do
next_state := addState(follow_pos);
(* merge transitions for the same next state: *)
mergeTrans;
(* sort transitions: *)
sortTrans;
endStateTrans;
end;
end(*makeDFATable*);
end(*LexDFA*).
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