ANTLR Hands on

Environments & Installation

Install JDK

Reference:

In Ubuntu:

1	sudo apt-get install openjdk-8-jre

In CentOS:

1	sudo yum install java-1.8.0-openjdk

In Mac OS:

Download jdk-8uversion-macosx-amd64.dmg and double click on it.

Check Java Version

$ java -version
java version "1.8.0_51"
Java(TM) SE Runtime Environment (build 1.8.0_51-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.51-b03, mixed mode)

Download ANTLR

1	wget http://www.antlr.org/download/antlr-3.5.2-complete.jar

Add this to the CLASSPATH:

1	export CLASSPATH=~/software/antlr-3.5.2-complete.jar:$CLASSPATH

Verify:

1
2
3

$ java org.antlr.Tool -version
ANTLR Parser Generator  Version 3.5.2

Tutorials

Refer:
links

$A Lexer$: This reads an input character or byte stream (i.e. characters, binary data, etc.), divides it into tokens using patterns you specify, and generates a token stream as output. It can also flag some tokens such as whitespace and comments as hidden using a protocol that ANTLR parsers automatically understand and respect.
$A Parser$: This reads a token stream (normally generated by a lexer), and matches phrases in your language via the rules (patterns) you specify, and typically performs some semantic action for each phrase (or sub-phrase) matched. Each match could invoke a custom action, write some text via StringTemplate, or generate an Abstract Syntax Tree for additional processing.

Create SimpleCalc.g:

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);
 
        SimpleCalcParser parser = new SimpleCalcParser(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 = HIDDEN; } ;
 
fragment DIGIT  : '0'..'9' ;

Run this file:

1	java org.antlr.Tool SimpleCalc.g

Then, we can find three generated files:

SimpleCalc.tokens, SimpleCalcParser.java and SimpleCalcLexer.java