@Test
public void testLookback() throws Exception {
LexerGrammar g =
new LexerGrammar(
"lexer grammar t;\n"
+ "ID : 'a'..'z'+;\n"
+ "INT : '0'..'9'+;\n"
+ "SEMI : ';';\n"
+ "ASSIGN : '=';\n"
+ "PLUS : '+';\n"
+ "MULT : '*';\n"
+ "WS : ' '+;\n");
// Tokens: 012345678901234567
// Input: x = 3 * 0 + 2 * 0;
CharStream input = new ANTLRInputStream("x = 3 * 0 + 2 * 0;");
LexerInterpreter lexEngine = g.createLexerInterpreter(input);
TokenStream tokens = createTokenStream(lexEngine);
tokens.consume(); // get x into buffer
Token t = tokens.LT(-1);
assertEquals("x", t.getText());
tokens.consume();
tokens.consume(); // consume '='
t = tokens.LT(-3);
assertEquals("x", t.getText());
t = tokens.LT(-2);
assertEquals(" ", t.getText());
t = tokens.LT(-1);
assertEquals("=", t.getText());
}
@Test
public void testCompleteBufferAfterConsuming() throws Exception {
LexerGrammar g =
new LexerGrammar(
"lexer grammar t;\n"
+ "ID : 'a'..'z'+;\n"
+ "INT : '0'..'9'+;\n"
+ "SEMI : ';';\n"
+ "ASSIGN : '=';\n"
+ "PLUS : '+';\n"
+ "MULT : '*';\n"
+ "WS : ' '+;\n");
// Tokens: 012345678901234567
// Input: x = 3 * 0 + 2 * 0;
CharStream input = new ANTLRInputStream("x = 3 * 0 + 2 * 0;");
LexerInterpreter lexEngine = g.createLexerInterpreter(input);
TokenStream tokens = createTokenStream(lexEngine);
Token t = tokens.LT(1);
while (t.getType() != Token.EOF) {
tokens.consume();
t = tokens.LT(1);
}
String result = tokens.getText();
String expecting = "x = 3 * 0 + 2 * 0;";
assertEquals(expecting, result);
}
@Test
public void test2ndToken() throws Exception {
LexerGrammar g =
new LexerGrammar(
"lexer grammar t;\n"
+ "ID : 'a'..'z'+;\n"
+ "INT : '0'..'9'+;\n"
+ "SEMI : ';';\n"
+ "ASSIGN : '=';\n"
+ "PLUS : '+';\n"
+ "MULT : '*';\n"
+ "WS : ' '+;\n");
// Tokens: 012345678901234567
// Input: x = 3 * 0 + 2 * 0;
CharStream input = new ANTLRInputStream("x = 3 * 0 + 2 * 0;");
LexerInterpreter lexEngine = g.createLexerInterpreter(input);
TokenStream tokens = createTokenStream(lexEngine);
String result = tokens.LT(2).getText();
String expecting = " ";
assertEquals(expecting, result);
}