Five minute introduction to ANTLR 3

This is the home page for the ANTLR 3 space.

What is ANTLR 3?

ANTLR 3 is the latest version of a language processing toolkit that was originally released as PCCTS in the mid-1990s. As was the case then, this release of the ANTLR toolkit advances the state of the art with it's new LL(*) parsing engine. ANTLR (ANother Tool for Language Recognition) provides a framework for the generation of recognizers, compilers, and translators from grammatical descriptions. ANTLR grammatical descriptions can optionally include action code written in what is termed the target language (i.e. the implementation language of the source code artifacts generated by ANTLR).

When it was released, PCCTS supported C as it's only target language, but through consulting with NeXT Computer, PCCTS supported C++ after 1994. It's immediate successor ANTLR 2 supported Java, C# and Python in addition to C++. Although it is still in beta, ANTLR 3 has already demonstrated support for Java, C#, Objective-C, C, C++ and Ruby as target languages. As of July 2006, the Java target is complete and the C#, Objective C, Ruby and C targets are nearly complete. Support for additional target languages including C++, Perl6 and Oberon (yes, Oberon) is either expected or already in progress.

What does ANTLR 3 do?

Put simply, ANTLR 3 generates - the source code for - language processing tools from a grammatical description. To this end, it is commonly categorised as a compiler generator or compiler compiler in the tradition of tools such as Lex/Flex and Yacc/Bison). ANTLR 3 can generate the source code for various tools that can be used to analyze and transform input in the language defined by the input grammar. The basic types of language processing tools that ANTLR can generates are Lexers (a.k.a scanners, tokenizers), Parsers and TreeParsers (a.k.a tree walkers, c.f. visitors).

Why should I use ANTLR 3?

Because it can save you time and resources by automating significant portions of the effort involved in building language processing tools. It is well established that generative tools such as compiler compilers have a major, positive impact on developer productivity. In addition, ANTLR v3's improved analysis engine, it's significantly enhanced parsing strength via LL(*) parsing with arbitrary lookahead, it's vastly improved tree construction rewrite rules and the availability of the simply fantastic AntlrWorks IDE offers productivity benefits over other comparable generative language processing toolkits.

How do I use ANTLR 3?

1. Get ANTLR 3

Download and install ANTLR 3 from the ANTLR 3 page of the ANTLR website

2. Run ANTLR 3 on a simple grammar

To be written. Volunteers?

2.1 Create a simple grammar

To be written. Volunteers?

grammar SimpleCalc;

tokens {
	PLUS 	= '+' ;
	MINUS	= '-' ;
	MULT	= '*' ;
	DIV	= '/' ;
}

@members {
    public static void main(String[] args) throws Exception {
        SimpleCalcLexer lex = new SimpleCalcLexer(new ANTLRFileStream(args[0]));
       	CommonTokenStream tokens = new CommonTokenStream(lex);

        SimpleCalc parser = new SimpleCalc(tokens);

        try {
            parser.expr();
        } catch (RecognitionException e)  {
            e.printStackTrace();
        }
    }
}

/*------------------------------------------------------------------
 * PARSER RULES
 *------------------------------------------------------------------*/

expr	: term ( ( PLUS | MINUS )  term )* ;
	
term	: factor ( ( MULT | DIV ) factor )* ;
	
factor	: NUMBER ;


/*------------------------------------------------------------------
 * LEXER RULES
 *------------------------------------------------------------------*/

NUMBER	: (DIGIT)+ ;
	
WHITESPACE : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ 	{ channel = 99; } ;
	
fragment DIGIT	: '0'..'9' ;

grammar SimpleCalc;

options {
    language=CSharp;
}

tokens {
	PLUS 	= '+' ;
	MINUS	= '-' ;
	MULT	= '*' ;
	DIV	= '/' ;
}

@members {
    public static void Main(string[] args) {
        SimpleCalcLexer lex = new SimpleCalcLexer(new ANTLRFileStream(args[0]));
       	CommonTokenStream tokens = new CommonTokenStream(lex);

        SimpleCalc parser = new SimpleCalc(tokens);

        try {
            parser.expr();
        } catch (RecognitionException e)  {
            Console.Error.WriteLine(e.StackTrace);
        }
    }
}

/*------------------------------------------------------------------
 * PARSER RULES
 *------------------------------------------------------------------*/

expr	: term ( ( PLUS | MINUS )  term )* ;
	
term	: factor ( ( MULT | DIV ) factor )* ;
	
factor	: NUMBER ;


/*------------------------------------------------------------------
 * LEXER RULES
 *------------------------------------------------------------------*/

NUMBER	: (DIGIT)+ ;
	
WHITESPACE : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ 	{ channel = 99; } ;
	
fragment DIGIT	: '0'..'9' ;

grammar Simple;

options 
{
    language=ObjC;
}

OR : '||' ;

grammar Simple;

options 
{
    language=C;
}

OR : '||' ;

2.2 Run ANTLR 3 on the simple grammar

To be written. Volunteers?

2.3 Revisit the simple grammar and learn basic ANTLR 3 syntax

To be written. Volunteers?

parser grammar Simple;

@header
{
    package antlr3.tutorial.simple;
}

OR : '||' ;

fragment DIGIT	: '0'..'9' ; 
NUMBER	: (DIGIT)+ ;

How about a more complex ANTLR 3 grammar?

To be written. Volunteers?

Sure, we'll use one from the examples-v3 distribution

What next?

Read the Antlr 3 Documentation

Browse the list of questions frequently asked about ANTLR 3

Try the AntlrWorks IDE for ANTLR 3. AntlrWorks can be downloaded from the AntlrWorks page on the ANTLR website

Your five minutes are up!

To be written. Volunteers?