Grammar definition problem.
Hi All,
I am facing problem in defining the following grammar for Bison.
X -> letter { letter | digit }.
here letter and digit are terminals and X is the non terminal symbol.
I am not able to put this rule in the bison grammar form hence need
some advice on this.
in particular I am not able to express the
letter AND {letter OR digit } rule in the Bison grammar.
how do I put the OR part of the rule inconsideration of the fact that
that scentence has to start with the "letter" and later have any
number of of digit?
Regards,
Atul.
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RE: Grammar definition problem.
Atul wrote:
> X -> letter { letter | digit }.
> here letter and digit are terminals and X is the non terminal symbol.
> how do I put the OR part of the rule inconsideration of the
> fact that that scentence has to start with the "letter" and
> later have any number of of digit?
Use a nonterminal symbol with a recursive rule to define your
{ letter | digit } part.
Ciao.Vincent.
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Re: %union errors that shouldn't be there
On Sun, 20 Mar 2005, DYP wrote: > In file included from misery.ll:30: > gram.yy:26: error: ISO C++ forbids declaration of `astNode' with no type > gram.yy:26: error: expected `;' before '*' token > gram.yy:27: error: ISO C++ forbids declaration of `string' with no type > gram.yy:27: error: expected `;' before '*' token > gram.yy:28: error: ISO C++ forbids declaration of `nodeList' with no > type > gram.yy:28: error: expected `;' before '*' token > Apparently, your types `astNode', `string', and `nodeList' are undefined when your `%union' declaration is being compiled. Assuming you're using C, My guess is that you're not including the header file or files that declare them in your parser input file. On the other hand, if you're using C++, it might be because these are types that can't be included in `unions'. I don't remember the rule off-hand --- it has something to do with constructors and/or destructors. I don't know whether this programming error would cause this particular compiler error to be signalled, though, and I don't have time to test this myself at the moment. Laurence Finston ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Grammar definition problem.
On Mon, 21 Mar 2005, Atul Kulkarni wrote: > how do I put the OR part of the rule inconsideration of the fact that > that scentence has to start with the "letter" and later have any > number of of digit? x: letter extension extension: /* Empty */ extension: extension letter extension: extension digit Laurence Finston ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Grammar definition problem.
In addition, note that most wold put this stuff in the lexer
(generated say by Flex).
At 14:55 +0530 2005/03/21, Atul Kulkarni wrote:
Hi All,
I am facing problem in defining the following grammar for Bison.
X -> letter { letter | digit }.
here letter and digit are terminals and X is the non terminal symbol.
I am not able to put this rule in the bison grammar form hence need
some advice on this.
in particular I am not able to express the
letter AND {letter OR digit } rule in the Bison grammar.
how do I put the OR part of the rule inconsideration of the fact that
that scentence has to start with the "letter" and later have any
number of of digit?
Regards,
Atul.
___
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Re: %union errors that shouldn't be there
At 11:55 +0100 2005/03/21, Laurence Finston wrote: On Sun, 20 Mar 2005, DYP wrote: In file included from misery.ll:30: gram.yy:26: error: ISO C++ forbids declaration of `astNode' with no type gram.yy:26: error: expected `;' before '*' token gram.yy:27: error: ISO C++ forbids declaration of `string' with no type gram.yy:27: error: expected `;' before '*' token gram.yy:28: error: ISO C++ forbids declaration of `nodeList' with no type gram.yy:28: error: expected `;' before '*' token Apparently, your types `astNode', `string', and `nodeList' are undefined when your `%union' declaration is being compiled. Assuming you're using C, My guess is that you're not including the header file or files that declare them in your parser input file. On the other hand, if you're using C++, it might be because these are types that can't be included in `unions'. I don't remember the rule off-hand --- it has something to do with constructors and/or destructors. I don't know whether this programming error would cause this particular compiler error to be signalled, though, and I don't have time to test this myself at the moment. They should be OK in C++, as pointers do not have non-trival con-/de-structors. The compiler needs to see a declaration of the name as a type, though, before it sees the pointer. -- Hans Aberg ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: %union errors that shouldn't be there
It looks as though the C++ compiler does not see the declaration of
the types astNode, string (is it std::string?), nodeList, before it
sees the union that the parser implements. So, you have to make sure
that info is included somewhere, perhaps in the %{ ... %} segment
before the %union in the .y file.
At 16:57 -0500 2005/03/20, DYP wrote:
Hello,
My %union is declared in the following way and does have the proper
header file included but I still get errors that should not be there.
%union{
float fconst;
int type;
astNode* node;
string* name;
nodeList* list;
}
Here are the errors that I get when trying to compile the bison
generated file
In file included from misery.ll:30:
gram.yy:26: error: ISO C++ forbids declaration of `astNode' with no type
gram.yy:26: error: expected `;' before '*' token
gram.yy:27: error: ISO C++ forbids declaration of `string' with no type
gram.yy:27: error: expected `;' before '*' token
gram.yy:28: error: ISO C++ forbids declaration of `nodeList' with no
type
gram.yy:28: error: expected `;' before '*' token
I just don't see what I am doing wrong.
Your help is appreciated.
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--
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RE: %union errors that shouldn't be there
Don't forget to cc Help-Bison, so others know that your problem has
been solved.
At 13:26 -0500 2005/03/21, Dmitry Podkuiko wrote:
Thanks for your response Hans. Indeed, it had do with #include's being in
the right order. The y.tab.h file has to be the last included and I had it
first in the list which caused it not to see the definitions of my classes
and even the std::string even though I included using namespace std;. Thank
You.
Dmitry.
-Original Message-
From: Hans Aberg [mailto:[EMAIL PROTECTED]
Sent: Monday, March 21, 2005 1:17 PM
To: [EMAIL PROTECTED]
Cc: help-bison@gnu.org
Subject: Re: %union errors that shouldn't be there
It looks as though the C++ compiler does not see the declaration of
the types astNode, string (is it std::string?), nodeList, before it
sees the union that the parser implements. So, you have to make sure
that info is included somewhere, perhaps in the %{ ... %} segment
before the %union in the .y file.
At 16:57 -0500 2005/03/20, DYP wrote:
Hello,
My %union is declared in the following way and does have the proper
header file included but I still get errors that should not be there.
%union{
float fconst;
int type;
astNode* node;
string* name;
nodeList* list;
}
Here are the errors that I get when trying to compile the bison
generated file
In file included from misery.ll:30:
gram.yy:26: error: ISO C++ forbids declaration of `astNode' with no type
gram.yy:26: error: expected `;' before '*' token
gram.yy:27: error: ISO C++ forbids declaration of `string' with no type
gram.yy:27: error: expected `;' before '*' token
gram.yy:28: error: ISO C++ forbids declaration of `nodeList' with no
type
gram.yy:28: error: expected `;' before '*' token
I just don't see what I am doing wrong.
Your help is appreciated.
___
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--
Hans Aberg
___
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RE: %union errors that shouldn't be there
Issue solved. It was the order in while y.tab.h was included in the flex
file.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Hans Aberg
Sent: Monday, March 21, 2005 1:32 PM
To: Dmitry Podkuiko
Cc: help-bison@gnu.org
Subject: RE: %union errors that shouldn't be there
Don't forget to cc Help-Bison, so others know that your problem has
been solved.
At 13:26 -0500 2005/03/21, Dmitry Podkuiko wrote:
>Thanks for your response Hans. Indeed, it had do with #include's being in
>the right order. The y.tab.h file has to be the last included and I had it
>first in the list which caused it not to see the definitions of my classes
>and even the std::string even though I included using namespace std;. Thank
>You.
>Dmitry.
>
>
>-Original Message-
>From: Hans Aberg [mailto:[EMAIL PROTECTED]
>Sent: Monday, March 21, 2005 1:17 PM
>To: [EMAIL PROTECTED]
>Cc: help-bison@gnu.org
>Subject: Re: %union errors that shouldn't be there
>
>It looks as though the C++ compiler does not see the declaration of
>the types astNode, string (is it std::string?), nodeList, before it
>sees the union that the parser implements. So, you have to make sure
>that info is included somewhere, perhaps in the %{ ... %} segment
>before the %union in the .y file.
>
>At 16:57 -0500 2005/03/20, DYP wrote:
>>Hello,
>>
>>My %union is declared in the following way and does have the proper
>>header file included but I still get errors that should not be there.
>>
>>%union{
>> float fconst;
>> int type;
>> astNode* node;
>> string* name;
>> nodeList* list;
>> }
>>
>>Here are the errors that I get when trying to compile the bison
>>generated file
>>
>>In file included from misery.ll:30:
>>gram.yy:26: error: ISO C++ forbids declaration of `astNode' with no type
>>gram.yy:26: error: expected `;' before '*' token
>>gram.yy:27: error: ISO C++ forbids declaration of `string' with no type
>>gram.yy:27: error: expected `;' before '*' token
>>gram.yy:28: error: ISO C++ forbids declaration of `nodeList' with no
>>type
>>gram.yy:28: error: expected `;' before '*' token
>>
>>I just don't see what I am doing wrong.
>>
>>Your help is appreciated.
>>
>>
>>
>>
>>___
>>Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
>
>
>--
>Hans Aberg
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