Wednesday, 6 June 2012

ANTLR as an external tool in eclipse on ubuntu

This tutorial tells how to setup the ANTLR in your eclipse.
STEP 1:
Download the jar file antlrworks-1.4.2.jar from http://www.antlr.org/download.
Further details about ANTLRWorks: The ANTLR GUI Development Environment, follow the link : http://www.antlr.org/works/index.html
STEP 2:
Create a java project in eclipse as follows:
File->New->Project
Select Java and Java project.
Click on Next.
Name the project as "TestANTLR"
Press Finish.
Add the antlrworks-1.4.2.jar to the project classpath.
Right click on "TestANTLR" project .
Select Properties->Libraries.
Click on "Add External jar"
Select the complete path of the "antlrworks-1.4.2.jar" and press Ok.
STEP 3: make it as an external tool
Goto Run->External Tools->Configure
Click on New.
Name: ANTLR Compiler
Tool Location: /usr/lib/jvm/java-6-sun-1.6.0.26/bin/java
// this must be the complete path to your java
Tool Arguments: -classpath complete_path_to_antlrworks-1.4.2.jar 

org.antlr.Tool ${resource_name}
Working Directory: ${container_loc}
Here, org.antlr.Tool is the main class which would take the ${resource_name} for processing.
${resource_name} and ${container_loc} can be selected with "Browse Variables" option too.

Going ahead :
*Creating a grammar file
Create a grammar file with .g extension. Say, Example.g

//sample code
grammar Example;
start : 'hello' ID ';' {System.out.println("hiii... "+$ID.text);} ;
ID: 'a'..'z' + ;
WS: (' ' |'\n' |'\r' )+
{$channel=HIDDEN;}


*Running the above code:
Run->External Tools->ANTLR Compiler
Press F5 or right click on the project and "refresh"
all you can see is a lexer and parser files generated with the tokens.


In our example,
ExampleLexer.java , ExampleParser.java and Example.tokens

Create Main.java program in the same project with the following code:

import org.antlr.runtime.*;
public class Main {
public static void main(String[] args) throws Exception {
// create a CharStream that reads from standard input
ANTLRInputStream input = new ANTLRInputStream(System.in);
// create a lexer that feeds off of input CharStream
ExampleLexer lexer = new ExampleLexer(input);
// create a buffer of tokens pulled from the lexer
CommonTokenStream tokens = new CommonTokenStream(lexer);
// create a parser that feeds off the tokens buffer
ExampleParser parser = new ExampleParser(tokens);
// begin parsing at rule start
parser.start();
}
}  


Set the arguments in the Run configurations and click on Apply and Run.
Now you have the output at console.
:)

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