antlr-3.4/tool/src/test/java/org/antlr/test/TestDFAMatching.java

/*
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 *  Copyright (c) 2010 Terence Parr
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package org.antlr.test;

import org.antlr.analysis.DFA;
import org.antlr.analysis.NFA;
import org.antlr.runtime.ANTLRStringStream;
import org.antlr.tool.Grammar;
import org.junit.Test;

public class TestDFAMatching extends BaseTest {

    /** Public default constructor used by TestRig */
    public TestDFAMatching() {
    }

    @Test public void testSimpleAltCharTest() throws Exception {
        Grammar g = new Grammar(
                "lexer grammar t;\n"+
                "A : {;}'a' | 'b' | 'c';");
		g.buildNFA();
		g.createLookaheadDFAs(false);
        DFA dfa = g.getLookaheadDFA(1);
        checkPrediction(dfa,"a",1);
        checkPrediction(dfa,"b",2);
        checkPrediction(dfa,"c",3);
        checkPrediction(dfa,"d", NFA.INVALID_ALT_NUMBER);
    }

    @Test public void testSets() throws Exception {
        Grammar g = new Grammar(
                "lexer grammar t;\n"+
                "A : {;}'a'..'z' | ';' | '0'..'9' ;");
		g.buildNFA();
        g.createLookaheadDFAs(false);
        DFA dfa = g.getLookaheadDFA(1);
        checkPrediction(dfa,"a",1);
        checkPrediction(dfa,"q",1);
        checkPrediction(dfa,"z",1);
        checkPrediction(dfa,";",2);
        checkPrediction(dfa,"9",3);
    }

    @Test public void testFiniteCommonLeftPrefixes() throws Exception {
        Grammar g = new Grammar(
                "lexer grammar t;\n"+
                "A : 'a' 'b' | 'a' 'c' | 'd' 'e' ;");
		g.buildNFA();
        g.createLookaheadDFAs(false);
        DFA dfa = g.getLookaheadDFA(1);
        checkPrediction(dfa,"ab",1);
        checkPrediction(dfa,"ac",2);
        checkPrediction(dfa,"de",3);
        checkPrediction(dfa,"q", NFA.INVALID_ALT_NUMBER);
    }

    @Test public void testSimpleLoops() throws Exception {
        Grammar g = new Grammar(
                "lexer grammar t;\n"+
                "A : (DIGIT)+ '.' DIGIT | (DIGIT)+ ;\n" +
                "fragment DIGIT : '0'..'9' ;\n");
		g.buildNFA();
        g.createLookaheadDFAs(false);
        DFA dfa = g.getLookaheadDFA(3);
        checkPrediction(dfa,"32",2);
        checkPrediction(dfa,"999.2",1);
        checkPrediction(dfa,".2", NFA.INVALID_ALT_NUMBER);
    }

    protected void checkPrediction(DFA dfa, String input, int expected)
        throws Exception
    {
        ANTLRStringStream stream = new ANTLRStringStream(input);
        assertEquals(dfa.predict(stream), expected);
    }

}