[antlr-interest] dynamic parsers

[Terence Parr]

On Nov 21, 2005, at 1:17 PM, Sergej Bogomolow wrote:

> I've got a question concerned dynamic parsers. Does
> antlr 3.0 make it possible to create dynamic parsers,
> i.e. intepreters?

You bet!  I'm going to make it even better.  Here is one of my  
functional tests:

	public void testSimpleParse() throws Exception {
		Grammar pg = new Grammar(
			"parser grammar p;\n"+
			"prog : WHILE ID LCURLY (assign)* RCURLY;\n" +
			"assign : ID ASSIGN expr SEMI ;\n" +
			"expr : INT | FLOAT | ID ;\n");
		Grammar g = new Grammar();
		g.importTokenVocabulary(pg);
		g.setGrammarContent(
			"lexer grammar t;\n"+
			"WHILE : \"while\";\n"+
			"LCURLY : '{';\n"+
			"RCURLY : '}';\n"+
			"ASSIGN : '=';\n"+
			"SEMI : ';';\n"+
			"ID : ('a'..'z')+ ;\n"+
			"INT : (DIGIT)+ ;\n"+
			"FLOAT : (DIGIT)+ '.' (DIGIT)* ;\n"+
			"fragment DIGIT : '0'..'9';\n" +
			"WS : (' ')+ ;\n");
		CharStream input = new ANTLRStringStream("while x { i=1; y=3.42;  
z=y; }");
		Interpreter lexEngine = new Interpreter(g, input);

		CommonTokenStream tokens = new CommonTokenStream(lexEngine);
		tokens.setTokenTypeChannel(g.getTokenType("WS"), 99);
		//System.out.println("tokens="+tokens.toString());
		Interpreter parseEngine = new Interpreter(pg, tokens);
		ParseTree t = parseEngine.parse("prog");
		String result = t.toStringTree();
		String expecting =
			"(<grammar p> (prog [@0,0:4='while',<4>,1:0] [@2,6:6='x',<5>,1:6]  
[@4,8:8='{',<6>,1:8] (assign [@6,10:10='i',<5>,1:10]  
[@7,11:11='=',<8>,1:11] (expr [@8,12:12='1',<10>,1:12])  
[@9,13:13=';',<9>,1:13]) (assign [@11,15:15='y',<5>,1:15]  
[@12,16:16='=',<8>,1:16] (expr [@13,17:20='3.42',<11>,1:17])  
[@14,21:21=';',<9>,1:21]) (assign [@16,23:23='z',<5>,1:23]  
[@17,24:24='=',<8>,1:24] (expr [@18,25:25='y',<5>,1:25])  
[@19,26:26=';',<9>,1:26]) [@21,28:28='}',<7>,1:28]))";
		assertEqual(result, expecting);
	}


I plan on making that really easy to just give me a few rules and  
have it do it's magic.

> I have my statechart grammar. If I use my program to
> translate this grammar, then I'll get ASt class files
> and a Antlr file.

Actually, I'm interpreting all that so it can't have actions but is  
much easier to use.

> Then I run antlr and the result is a
> parser. In the next step this parser should be
> compiled. Is it possible to create a dynamic parser
> which intepret the statechart grammar on the fly using
> antlr 3.0?

You can easily compile and run antlr parsers on the fly as every one  
of my function tests do this.  See the TestCompileAndExecSupport.java  
file in the v3 distribution.

> It is important to point that the Java
> parser must be available in the compiled form at the
> end of the process.

No problem :)

Ter