[antlr-interest] - Python Target

[Benjamin Niemann]

Edward Hartley wrote:

>> I'm looking at the example grammar Expr.g from the book and when testing
>> it with valid expressions like (3+4)*9 I get the output like the
>> following
>>>>> (3+4)*9
>> line 0:-1 mismatched input '<EOF>' expecting NEWLINE
>>
>> Is this behaviour correct or is it due to my having missed something:
>> I retained the skip() call in the  NEWLINE rule.
>> I don not get this behavior with the Java target and see the same as is
>> described in the book.
> 
> I can't reproduce this. Are you sure that the input actually has a '\n' at
> the end? How does your main script look like?
> 
> 
> 
> My Driver program looks like this:
> 
> import antlr3
> from ExprLexer import ExprLexer
> from ExprParser import ExprParser
> 
> while True:
>     expr = raw_input('>>> ')
>     if expr == "'':
>         break
>     cStream = antlr3.StringStream(expr)
>     lexer = ExprLexer(cStream)
>     tStream = antlr3.CommonTokenStream(lexer)
>     parser = ExprParser(tStream)
>     parser.prog()
> 
> I'm a bit mystified and expect I've missed something blindingly obvious.

The result of raw_input() does not include the '\n'. But in this grammar,
every line must be terminated by NEWLINE.
Either change the grammar (with raw_input() you are not able to read
multiline input anyway) or add a '\n' to the input before you feed it into
ANTLR.

-- 
Benjamin Niemann
Email: pink at odahoda dot de
WWW: http://pink.odahoda.de/