Re: how to get left hand side symbol in action

[Christian Schoenebeck]

On Donnerstag, 9. Mai 2019 08:50:27 CEST Akim Demaille wrote:
> > 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.

That's actually a very common required feature in practice. The main use cases 
are:

1. Auto completion features

2. Human friendly error messages

I do need these features for almost all parsers, hence for years (since not 
available directly with Bison) I have a huge bunch of code on top of the 
internal skeleton code to achieve them. With the obvious problems:

- since based on skeleton internals, that extra code might break with new 
  Bison version (which it did already several times)

- since the generated parser tables are a compressed representation of the 
  grammar, designed just to resolve grammar rules efficiently at runtime,
  hence information is missing for the tasks above that must be extra polated 
  with additional custom code to achieve those feature ATM

> 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?

In practice you just need the symbol name as is. Nobody needs the translation, 
or if somebody really needs it, then anybody can achieve this very, very 
easily on its own. That's trivial.

The main reason why people are asking for support on Bison side for the 
features discussed here is that it is currently not trivial to achieve them 
with own, custom code. You do need to have a profound knowledge of how the 
internal skeleton algorithm works to be able to extra polate the missing 
information by custom code on top of it.

Best regards,
Christian Schoenebeck