Re: %left is not working

[Chris verBurg]

I think I see a few issues in your code, but without the complete source I
can't conclusively say what your problem might be.

First:
>   if(strcmp($<blOperator>2, "+"))
Just to be sure: you know strcmp returns 0 when the strings match, right?  I
ask because it looks like you're trying to convert "+" to "add", and this
logic will convert it to "sub".

Next:
>       strcpy($<blOperator>2, "add");
I don't think it's really safe to write to a $k variable.  Granted if you
own its type you can do whatever you want, but that's not the case here.
 You show that it's created by strdup, but if the value is "+" then the char
string is only two characters long -- you can't safely strcpy the
four-character "add" string to that location.

Next:
> | ( expr)
As Hans mentioned, there's a default action here to return the $1 value as
$$, and that's not what you want.  You'll need to make an explicit action to
return $2 instead.  Oh, I see he just posted that.  :)

Related to that, you don't assign $$ in the "expr" rule at all.  Instead you
seem to be trying to overwrite $1.  Since "expr" is recursive, you'll have
to assign $$ in order to propagate values correctly up the stack.


Hope that helps.. :/
-Chris



On Wed, Aug 4, 2010 at 9:39 AM, Sasan Forghani <address@hidden>wrote:

> Thank you for the information.  However, how does this relate to the
> $<blIdentifier> problem I am having.  To be more specific, the problem
> where
> the $<blIdentifier> of the ASSIGNMENT production ends up with the same
> value
> of the ( expr ) production.
>
> On Wed, Aug 4, 2010 at 9:04 AM, Hans Aberg <address@hidden> wrote:
>
> > On 4 Aug 2010, at 14:17, Sasan Forghani wrote:
> >
> >  I apologize for my lack of understanding.  You said the next step is to
> >> clean it up in the actions... please clarify?
> >>
> >
> > When you allocate stuff using malloc, strdup, etc. when pointer is not
> used
> > anymore, to avoid memory leak, one must apply free(). For example, an
> action
> > might look like
> >  $$ = malloc(...) // pr something
> >  // copy over some stuff from the $k values.
> > Now the, $k values are not used anymore - only $$, so they must be
> cleaned
> > up using free().
> >
> > This works if you do not want to do error recovery. For that there is a
> > special function (see the Bison manual).
> >
> > I do not program in C, but C++, where the language is taking care of
> this.
> > So perhaps some else might give better examples.
> >
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