Re: too many warnings from Bison CVS for Pike

[Joel E. Denny]

On Sun, 29 Jan 2006, Hans Aberg wrote:

> On 29 Jan 2006, at 20:11, Joel E. Denny wrote:
> 
> > >   %define pre-switch { if (yylen >= 1)  $$ = $1; }
> > 
> > This isn't yacc compatible.
> 
> That depends on the interpretation of the Yacc specification.

???

> If I look for other uses of the word "default" and the wording "by default",
> it means "in the case no other explicit directions has been given". So "By
> default, the value of a rule shall be the value of the first element in it."
> means that this is the value if no other explicit value has been given, and if
> such an explicit value has been given, the default rules does not apply.
> 
> This is still unclear, because one can write a rule action explicitly as {}.

Which doesn't give any `explicit directions' for the value for the rule.

> Should then $$ = $1 be applied? 

Under yacc, I'm saying yes.

> - There is a difference between explicitly
> indicating a rule action, and explicitly assigning a value to $$.

That's exactly my point.

Anyway, we can debate this all week and get no where.  I think Paul's 
point is valid: regardless of what the Open Group says, executing $$ = $1 
before explicit actions will offer the widest compatibility with existing 
yacc grammars.  I say we simply state our interpretation of the spec, and 
use that interpretation as the justification for handling this with 
--yacc.

Joel