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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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* Copyright (C) 1998-2001 Gerwin Klein <lsf@jflex.de> *
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* All rights reserved. *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License. See the file *
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* COPYRIGHT for more information. *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* You should have received a copy of the GNU General Public License along *
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* with this program; if not, write to the Free Software Foundation, Inc., *
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA *
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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* Performs simple semantic analysis on regular expressions.
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* (used for checking if trailing contexts are legal)
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* @author Gerwin Klein
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* @version JFlex 1.3.5, $Revision: 1.15 $, $Date: 2001/10/08 10:08:05 $
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public final class SemCheck {
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// stored globally since they are used as constants in all checks
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private static Macros macros;
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private static char maxChar;
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* Performs semantic analysis for all expressions.
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* Currently: illegal lookahead check only
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* [fixme: more checks possible]
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* @param rs the reg exps to be checked
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* @param m the macro table (in expanded form)
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* @param max max character of the used charset (for negation)
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* @param f the spec file containing the rules [fixme]
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public static void check(RegExps rs, Macros m, char max, File f) {
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boolean errors = false;
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int num = rs.getNum();
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for (int i = 0; i < num; i++) {
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RegExp r = rs.getRegExp(i);
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RegExp l = rs.getLookAhead(i);
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if (!checkLookAhead(r,l)) {
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Out.error(f, ErrorMessages.LOOKAHEAD_ERROR, rs.getLine(i), -1);
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if (errors) throw new GeneratorException();
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* Checks for illegal lookahead expressions.
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* Lookahead in JFlex only works when the first expression has fixed
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* length or when the intersection of the last set of the first expression
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* and the first set of the second expression is empty.
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* @param r1 first regexp
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* @param r2 second regexp (the lookahead)
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* @return true iff JFlex can generate code for the lookahead expression
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private static boolean checkLookAhead(RegExp r1, RegExp r2) {
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return r2 == null || length(r1) > 0 || !(last(r1).and(first(r2)).containsElements());
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* Returns length if expression has fixed length, -1 otherwise.
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private static int length(RegExp re) {
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int l1 = length(r.r1);
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if (l1 < 0) return -1;
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int l2 = length(r.r2);
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int l1 = length(r.r1);
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if (l1 < 0) return -1;
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int l2 = length(r.r2);
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if (l2 < 0) return -1;
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String content = (String) ((RegExp1) re).content;
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return content.length();
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return length(macros.getDefinition((String) ((RegExp1) re).content));
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throw new Error("Unkown expression type "+re.type+" in "+re);
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* Returns true iff the matched language contains epsilon
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private static boolean containsEpsilon(RegExp re) {
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return containsEpsilon(r.r1) || containsEpsilon(r.r2);
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if (containsEpsilon(r.r1))
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return containsEpsilon(r.r2);
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return containsEpsilon( (RegExp) ((RegExp1)re).content );
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return ((String) ((RegExp1) re).content).length() <= 0;
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return containsEpsilon(macros.getDefinition((String) ((RegExp1) re).content));
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throw new Error("Unkown expression type "+re.type+" in "+re);
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* Returns the first set of an expression.
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* (the first-character-projection of the language)
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private static IntCharSet first(RegExp re) {
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return first(r.r1).add(first(r.r2));
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if ( containsEpsilon(r.r1) )
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return first(r.r1).add(first(r.r2));
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return first((RegExp) ((RegExp1)re).content);
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return new IntCharSet((Vector) ((RegExp1) re).content);
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IntCharSet all = new IntCharSet(new Intervall( (char) 0,maxChar));
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IntCharSet set = new IntCharSet((Vector) ((RegExp1) re).content);
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return new IntCharSet(((Character) ((RegExp1) re).content).charValue());
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String content = (String) ((RegExp1) re).content;
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if (content.length() > 0)
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return new IntCharSet(content.charAt(0));
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return new IntCharSet();
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return first(macros.getDefinition((String) ((RegExp1) re).content));
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throw new Error("Unkown expression type "+re.type+" in "+re);
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* Returns the last set of the expression
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* (the last-charater-projection of the language)
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private static IntCharSet last(RegExp re) {
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return last(r.r1).add(last(r.r2));
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if ( containsEpsilon(r.r2) )
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return last(r.r1).add(last(r.r2));
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return last((RegExp) ((RegExp1)re).content);
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return new IntCharSet((Vector) ((RegExp1) re).content);
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IntCharSet all = new IntCharSet(new Intervall( (char) 0,maxChar));
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IntCharSet set = new IntCharSet((Vector) ((RegExp1) re).content);
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return new IntCharSet(((Character) ((RegExp1) re).content).charValue());
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String content = (String) ((RegExp1) re).content;
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if (content.length() > 0)
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return new IntCharSet(content.charAt(content.length()-1));
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return new IntCharSet();
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return last(macros.getDefinition((String) ((RegExp1) re).content));
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throw new Error("Unkown expression type "+re.type+" in "+re);
added
removed
src/JFlex/SemCheck.java
