[antlr-interest] COBOL grammar

[Parsiad Azimzadeh]

Apologies, I seemed to have not been thinking when I wrote my last email. If
you were to use

block: (command END_BLOCK)*;

the END_BLOCK command would be paired with each command. What I was trying
to say was:

block: command* END_BLOCK;

Note that your END_BLOCK token has to differ from '.', otherwise you will
introduce another ambiguity.

-- 
Parsiad Azimzadeh
http://sfu.ca/~paa4

On Mon, Jul 11, 2011 at 1:46 PM, Nilo Roberto C Paim <nilopaim at gmail.com>wrote:

> Thanks, Parsiad, for your help.
>
> Indeed the ambiguities are 'solved'... but using your solution, only the
> first 'command' of the first 'block' of the first 'paragraph' are parsed!
>
> And I don't have something I can call 'END_BLOCK', as you suggested. This
> thing would be a '.', that can be preceded by a 'command' either... and the
> problem returns...
>
> What else am I missing?
>
> TIA,
> Nilo - Brazil
>
> -----Mensagem original-----
> De: antlr-interest-bounces at antlr.org
> [mailto:antlr-interest-bounces at antlr.org] Em nome de Parsiad Azimzadeh
> Enviada em: segunda-feira, 11 de julho de 2011 14:36
> Para: antlr-interest at antlr.org
> Assunto: Re: [antlr-interest] COBOL grammar
>
> Hi Nilo,
>
> The problem is that a paragraph contains any number of blocks and a block
> contains any number of commands (the ambiguity here is that some paragraph
> with two commands can be perceived as containing either two blocks each
> with
> one command or a single block with two commands).
>
> The fix is simple, remove the * symbol from the line:
> paragraph : ID '.' block* '.';
>
> If multiple blocks holds semantic value, you might need to use a symbol to
> denote the end of a block. For example, instead of using the fix above you
> could change the block rule to:
>
> block: (command END_BLOCK)*;
>
> --
> Parsiad Azimzadeh
> http://sfu.ca/~paa4
>
> On Mon, Jul 11, 2011 at 9:46 AM, Nilo Roberto C Paim
> <nilopaim at gmail.com>wrote:
>
> > Hi all,
> >
> > I'm facing a problem on my grammar that I don't know how to solve
> > (Antlr3.3)...
> >
> > Let me show you my grammar. Simplified, of course. It's just to show you
> my
> > trouble.
> >
> >
> >
> >
> >
> > grammar Cobol;
> >
> > options {
> >  language = Java;
> > }
> >
> > program : 'procedure' 'division' '.' section*;
> >
> > section : ID 'section' '.' paragraph*;
> >
> > paragraph : ID '.' block* '.';
> >
> > block : command*;
> >
> > command: (cmdA | cmdB | cmdC ) '.'?;
> >
> > cmdA: 'A';
> >
> > cmdB: 'B';
> >
> > cmdC: 'C';
> >
> > fragment Digit : '0'..'9';
> >
> > fragment Letter : ('a'..'z' | 'A'..'Z');
> >
> > ID : Letter ( Letter | Digit | '-' )*;
> >
> >
> >
> >
> >
> > Using this grammar, I'm having the following errors and warnings:
> >
> > warning(200): /Cobol/src/Cobol.g:14:12: Decision can match input such as
> > "{'.', 'A'..'C'}" using multiple alternatives: 1, 2
> > As a result, alternative(s) 2 were disabled for that input
> >  |---> ID '.' block* '.';
> >
> > error(201): /Cobol/src/Cobol.g:14:12: The following alternatives can
> never
> > be matched: 2
> >  |---> ID '.' block* '.';
> >
> > warning(200): /Cobol/src/Cobol.g:17:5: Decision can match input such as
> > "'B'" using multiple alternatives: 1, 2
> > As a result, alternative(s) 2 were disabled for that input
> >  |---> command*;
> >
> > warning(200): /Cobol/src/Cobol.g:17:5: Decision can match input such as
> > "'A'" using multiple alternatives: 1, 2
> > As a result, alternative(s) 2 were disabled for that input
> >  |---> command*;
> >
> > warning(200): /Cobol/src/Cobol.g:17:5: Decision can match input such as
> > "'C'" using multiple alternatives: 1, 2
> > As a result, alternative(s) 2 were disabled for that input
> >  |---> command*;
> >
> >
> > 4 warnings
> >
> > 1 error
> >
> > BUILD FAIL
> >
> >
> >
> > My real problem is:
> >
> > 1) any 'command' can be followed by a '.'
> > 2) any sequence of 'command's not followed by '.' forms a 'block'
> > 3) wherever I can use a 'command', I can use a 'block'
> > 4) the '.' signifies the end of a 'block'
> > 5) I can use any number of 'block's to form a 'paragraph'
> > 6) I can use any number of 'paragraph's to form a 'section'
> > 7) I can have any number of 'section's on a 'program'
> >
> > Any hints or help about what am I doing wrong? I'm completely stuck on
> it,
> > 'cause I'm a little newbie using Antlr...
> >
> > TIA,
> > Nilo - Brazil
> >
> >
> > List: http://www.antlr.org/mailman/listinfo/antlr-interest
> > Unsubscribe:
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> >
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