Re: how to get left hand side symbol in action

> On 9 May 2019, at 08:50, Akim Demaille <[email protected]> wrote:
> 
>> Le 6 mai 2019 à 22:45, Hans Åberg <[email protected]> a écrit :
>> 
>>> On 6 May 2019, at 18:09, Akim Demaille <[email protected]> wrote:
>>> 
>>>> Le 6 mai 2019 à 14:50, Hans Åberg <[email protected]> a écrit :
>>>> 
>>>>> On 6 May 2019, at 11:28, r0ller <[email protected]> wrote:
>>>>> 
>>>>> Hi All,
>>>>> 
>>>>> Is it possible in *any* way to get the left hand side symbol in an action of a rule? Say, I have:
>>>>> 
>>>>> A : B C
>>>>> {<!-- -->
>>>>> std:cout<<"left hand side symbol is:"<<???
>>>>> };
>>>>> 
>>>>> I tried to find it out myself and googled a lot but didn't find anything:(
>>>> 
>>>> In the C++ parser, one can write:
>>>> std::cout << “LHS: " << yytname_[yylhs.type_get()] << std::endl;
>>> 
>>> But it's an internal detail, there is no guarantee it won't change.
>> 
>> Right, so it might be a feature request for the longer term.
> 
> I'm trying to see what would make sense.
> 
>> Perhaps a variation of $ and @ that gives access to the name,
> 
> I am very uncomfortable with this.  Symbol names are technical details,
> most of the time they are irrelevant to the end user, just like the
> the user of a piece of software does not care about the names of the
> functions: that's a implementation detail.
> 
> In addition, tokens have several names: the identifier, and the
> string name, like
> 
> %token <string> ID "identifier"
> 
> Not to mention that I also want to provide support for
> internationalization.  So what name should that be? ID?
> identifier? or identifiant in French?
> 
> Of course when you debug a grammar, the names of the symbols
> are very important, and that's why the debug traces need the
> symbol names.  Again, like when you debug a program: then
> function names matter.
> 
> In the present case, I believe that the names that r0ller want
> should really be part of *his* specification, they should
> not come from internal details such as the symbol name.  So
> I do think it is saner that the names are explicitly put in the
> action.
> 
>> or the raw stack value in case there are more stuff to access.
> 
> Which only exists in lalr1.cc.  And I think r0ller is using
> glr.cc.  Maybe once Valentin is done there will be symbols.

Perhaps it is best to see what he wants, which looks complicated, and perhaps provide something more stable. I can’t recall any other request for the grammar variable names.



_______________________________________________
[email protected] https://lists.gnu.org/mailman/listinfo/help-bison