What's wrong with this example ANTLR 3 Python grammer? -

i'm trying learn use antlr, , seem have come across error while following "tutorial": https://theantlrguy.atlassian.net/wiki/display/antlr3/five+minute+introduction+to+antlr+3

essentially, create file simplecalc.g:

grammar simplecalc;   options {     language = python; }   tokens {     plus    = '+' ;     minus   = '-' ;     mult    = '*' ;     div = '/' ; }   @header { import sys import traceback   simplecalclexer import simplecalclexer }   @main { def main(argv, otherarg=none):   char_stream = antlrfilestream(sys.argv[1])   lexer = simplecalclexer(char_stream)   tokens = commontokenstream(lexer)   parser = simplecalcparser(tokens);     try:         parser.expr()   except recognitionexception:     traceback.print_stack() }   /*------------------------------------------------------------------  * 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' ; 

when run antlr tools

 java -classpath antlr-3.1.3.jar antlr.tool simplecalc.g 

i receive errors, starting first line:

antlr parser generator   version 2.7.7 (20060906)   1989-2005 simplecalc.g:2:1: unexpected token: grammar error: token stream error reading grammar(s): simplecalc.g:15:1: unexpected char: '@' simplecalc.g:2:1: rule grammar trapped: simplecalc.g:2:1: unexpected token: grammar tokenstreamexception: unexpected char: '@' 

this leads me believe i'm doing stupid, i'm not sure what. matter appreciated.

thanks,
chris covert

you're using wrong tool class generate lexer , parser. antlr 3.x versions still have dependencies older v2.7 version, therefor included in v3.x. tool class v2.7 called antlr.tool, while v3.x version called org.antlr.tool. latter 1 should using:

java -classpath antlr-3.1.3.jar org.antlr.tool simplecalc.g 

edit

here's little demo based on grammar wiki, bit of python code added evaluates expression:

grammar simplecalc;  options {   language=python; }  @header { import sys import traceback  simplecalclexer import simplecalclexer }  @main { def main(argv, otherarg=none):   char_stream = antlrstringstream(sys.argv[1])   lexer = simplecalclexer(char_stream)   tokens = commontokenstream(lexer)   parser = simplecalcparser(tokens);    try:     print parser.eval()   except recognitionexception:     traceback.print_stack() }  eval returns [value]  : add eof {$value = $add.value}  ;  add returns [value]  : m1=mult {$value = $m1.value} ( '+' m2=mult {$value += $m2.value}                                 | '-' m2=mult {$value -= $m2.value}                                 )*   ;  mult returns [value]  : a1=atom {$value = $a1.value} ( '*' a2=atom {$value *= $a2.value}                                 | '/' a2=atom {$value /= $a2.value}                                 )*   ;  atom returns [value]  : number      {$value = float($number.text)}  | '(' add ')' {$value = $add.value}  ;  number         : digit+ ('.' digit*)?; whitespace     : ('\t' | ' ' | '\r' | '\n')+ {$channel = hidden;}; fragment digit : '0'..'9' ; 

generating lexer/parser , evaluating expression:

java -cp antlr-3.1.3.jar org.antlr.tool simplecalc.g python simplecalcparser.py "5 * (8 + 2)" 

produces output:

50.0