Page Comparison

grammar MExpr;

options {
  language = Perl5;
}

prog:   stat+ ;

stat:   expr NEWLINE { print "$expr.value\n"; }
    |   NEWLINE
    ;

expr returns [value]
    :   e=atom { $value = $e.value; }
        (   '+' e=atom { $value += $e.value; }
        |   '-' e=atom { $value -= $e.value; }
        )*
    ;

atom returns [value]
    :   INT { $value = $INT.text; }
    |   '(' expr ')' { $value = $expr.value; }
    ;

ID  :   ('a'..'z'|'A'..'Z')+ ;
INT :   '0'..'9'+ ;
NEWLINE:'\r'? '\n' ;
WS  :   (' '|'\t')+ { \$self->skip(); } ;

#!/usr/bin/perl

use strict;
use warnings;

use ANTLR::Runtime::ANTLRStringStream;
use ANTLR::Runtime::CommonTokenStream;
use MExprLexer;
use MExprParser;

while (<>) {
    my $input = ANTLR::Runtime::ANTLRStringStream->new($_);
    my $lexer = MExprLexer->new($input);

    my $tokens = ANTLR::Runtime::CommonTokenStream->new({ token_source => $lexer });
    my $parser = MExprParser->new($tokens);
    $parser->prog();
}