testsemanticpredicateevaluation.java

ANTLR(ANother Tool for Language Recognition)它是这样的一种工具

/*
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Copyright (c) 2005-2006 Terence Parr
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package org.antlr.test;

public class TestSemanticPredicateEvaluation extends BaseTest {
	public void testSimpleCyclicDFAWithPredicate() throws Exception {
		String grammar =
			"grammar foo;\n" +
			"a : {false}? 'x'* 'y' {System.out.println(\"alt1\");}\n" +
			"  | {true}?  'x'* 'y' {System.out.println(\"alt2\");}\n" +
			"  ;\n" ;
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "xxxy", false);
		assertEquals("alt2\n", found);
	}

	public void testSimpleCyclicDFAWithInstanceVarPredicate() throws Exception {
		String grammar =
			"grammar foo;\n" +
			"@members {boolean v=true;}\n" +
			"a : {false}? 'x'* 'y' {System.out.println(\"alt1\");}\n" +
			"  | {v}?     'x'* 'y' {System.out.println(\"alt2\");}\n" +
			"  ;\n" ;
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "xxxy", false);
		assertEquals("alt2\n", found);
	}

	public void testPredicateValidation() throws Exception {
		String grammar =
			"grammar foo;\n" +
			"@members {\n" +
			"public void reportError(RecognitionException e) {\n" +
			"    System.out.println(\"error: \"+e.toString());\n" +
			"}\n" +
			"}\n" +
			"\n" +
			"a : {false}? 'x'\n" +
			"  ;\n" ;
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "x", false);
		assertEquals("error: FailedPredicateException(a,{false}?)\n", found);
	}

	public void testLexerPreds() throws Exception {
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=false;}\n" +
			"a : (A|B)+ ;\n" +
			"A : {p}? 'a'  {System.out.println(\"token 1\");} ;\n" +
			"B : {!p}? 'a' {System.out.println(\"token 2\");} ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "a", false);
		// "a" is ambig; can match both A, B.  Pred says match 2
		assertEquals("token 2\n", found);
	}

	public void testLexerPreds2() throws Exception {
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=true;}\n" +
			"a : (A|B)+ ;\n" +
			"A : {p}? 'a' {System.out.println(\"token 1\");} ;\n" +
			"B : ('a'|'b')+ {System.out.println(\"token 2\");} ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "a", false);
		// "a" is ambig; can match both A, B.  Pred says match 1
		assertEquals("token 1\n", found);
	}

	public void testLexerPredInExitBranch() throws Exception {
		// p says it's ok to exit; it has precendence over the !p loopback branch
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=true;}\n" +
			"a : (A|B)+ ;\n" +
			"A : ('a' {System.out.print(\"1\");})*\n" +
			"    {p}?\n" +
			"    ('a' {System.out.print(\"2\");})* ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aaa", false);
		assertEquals("222\n", found);
	}

	public void testLexerPredInExitBranch2() throws Exception {
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=true;}\n" +
			"a : (A|B)+ ;\n" +
			"A : ({p}? 'a' {System.out.print(\"1\");})*\n" +
			"    ('a' {System.out.print(\"2\");})* ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aaa", false);
		assertEquals("111\n", found);
	}

	public void testLexerPredInExitBranch3() throws Exception {
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=true;}\n" +
			"a : (A|B)+ ;\n" +
			"A : ({p}? 'a' {System.out.print(\"1\");} | )\n" +
			"    ('a' {System.out.print(\"2\");})* ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aaa", false);
		assertEquals("122\n", found);
	}

	public void testLexerPredInExitBranch4() throws Exception {
		String grammar =
			"grammar foo;" +
			"a : (A|B)+ ;\n" +
			"A @init {int n=0;} : ({n<2}? 'a' {System.out.print(n++);})+\n" +
			"    ('a' {System.out.print(\"x\");})* ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aaaaa", false);
		assertEquals("01xxx\n", found);
	}

	public void testLexerPredsInCyclicDFA() throws Exception {
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=false;}\n" +
			"a : (A|B)+ ;\n" +
			"A : {p}? ('a')+ 'x'  {System.out.println(\"token 1\");} ;\n" +
			"B :      ('a')+ 'x' {System.out.println(\"token 2\");} ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aax", false);
		assertEquals("token 2\n", found);
	}

	public void testLexerPredsInCyclicDFA2() throws Exception {
		String grammar =
			"grammar foo;" +
			"@lexer::members {boolean p=false;}\n" +
			"a : (A|B)+ ;\n" +
			"A : {p}? ('a')+ 'x' ('y')? {System.out.println(\"token 1\");} ;\n" +
			"B :      ('a')+ 'x' {System.out.println(\"token 2\");} ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aax", false);
		assertEquals("token 2\n", found);
	}

	public void testGatedPred() throws Exception {
		String grammar =
			"grammar foo;" +
			"a : (A|B)+ ;\n" +
			"A : {true}?=> 'a' {System.out.println(\"token 1\");} ;\n" +
			"B : {false}?=>('a'|'b')+ {System.out.println(\"token 2\");} ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aa", false);
		// "a" is ambig; can match both A, B.  Pred says match A twice
		assertEquals("token 1\ntoken 1\n", found);
	}

	public void testGatedPred2() throws Exception {
		String grammar =
			"grammar foo;\n" +
			"@lexer::members {boolean sig=false;}\n"+
			"a : (A|B)+ ;\n" +
			"A : 'a' {System.out.print(\"A\"); sig=true;} ;\n" +
			"B : 'b' ;\n" +
			"C : {sig}?=> ('a'|'b') {System.out.print(\"C\");} ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aa", false);
		assertEquals("AC\n", found);
	}

	public void testPredWithActionTranslation() throws Exception {
		String grammar =
			"grammar foo;\n" +
			"a : b[2] ;\n" +
			"b[int i]\n" +
			"  : {$i==1}?   'a' {System.out.println(\"alt 1\");}\n" +
			"  | {$b.i==2}? 'a' {System.out.println(\"alt 2\");}\n" +
			"  ;\n";
		String found = execParser("foo.g", grammar, "fooParser", "fooLexer",
				    "a", "aa", false);
		assertEquals("alt 2\n", found);
	}


	// S U P P O R T

	public void _test() throws Exception {
		String grammar =
			"grammar T;\n" +
			"options {output=AST;}\n" +
			"a :  ;\n" +
			"ID : 'a'..'z'+ ;\n" +
			"INT : '0'..'9'+;\n" +
			"WS : (' '|'\\n') {channel=99;} ;\n";
		String found = execParser("t.g", grammar, "T", "TLexer",
				    "a", "abc 34", false);
		assertEquals("\n", found);
	}

}