Re: Using bison (or bisonc++) to create parser for command completion

[Hans Aberg]

On 4 Feb 2009, at 03:40, José Alburquerque wrote:

> Hi.  I'm not subscribed to this list, but I'm hoping someone here  
> can still help me.  I'm attempting to develop a small front-end to  
> dvdauthor  in C++ to logically create DVD's to be played in standard  
> DVD players. I would like to include "command completion"  
> functionality in an area of the GUI for accepting low level commands  
> to the DVD player based on a very simple language, already specified  
> for this purpose by the dvdauthor developers (if I'm not mistaken) 
> [1].  All I'm really asking for, if possible, is clarification on  
> whether bison can be used to create a parser for the simple language  
> and then somehow use the parser to tell what might come after  
> certain keywords.  If so, is it straight forward?  Finally, I've  
> looked a bit at bisonc++ and am wondering if it can be used instead  
> of bison for the same purposes (I'd rather have C++ classes, if  
> possible).  Please, any clarification would be greatly appreciated.

You can use the .output file that Bison generates to get a set of  
possible tokens for each state. The look at the top of the state stack  
in the parser that Bison generates, and present that. Not in any  
automated fashion, though, as far as I know.

One problem is that the LALR(1) parsing algorithm that Bison uses  
makes state compaction which may admit some reductions before a state  
where the error/lookahead tokens appears. So this method may note be  
correct - strictly speaking, one should use LR(1). But the problem may  
not be too severe.

  Hans