Re: indentations instead of endtag in a grammar

[Hans Aberg]

On 17 Feb 2010, at 14:12, Andreas Wagner wrote:

> The source code that I have to parse loks more like:
>
> if(signal):
>  variable_a := do_something
> else:
>  variable_b := do_something_other
>
> variable_c := signal_x;
>
> How can i tell Bison that that it has to look for the indentations?  
> Has
> anyone maybe an example that he/she can send me ? it would be very  
> helpful,
> because i havent seen such an example.

You might look into the sources of the Haskell interpreter Hugs <http://haskell.org/hugs/ 
>, which I recall uses .y files. (Haskell admits layout syntax.)

My guess is though that you have to put a rule in the .l file that  
recognizes the indentation, that is to be recognized.

If the syntax is good, it might be possible to do it with sufficient  
lookahead ( a different type of language specification). There the GLR  
parser might be used (se the Bison manual).

  Hans