Re: Problems with epsilon productions

[Hans Aberg]

On 17 Oct 2005, at 23:57, Arlen Cox wrote:

> I am trying to implement a grammar that may have 0 or more of a  
> construct.
> Effectively I want to have a grammar like this:
>
> File:
>     ( Module )*
>
> I've looked through the manual and it appears bison does not  
> support this
> construct,

Right, Bison doesn't support that.

> I was trying to replicate it.  I've tried two ways:

Waite & Goos, "Compiler construction", gives the following rewritings
  Abbreviation               Meaning
  x -> alpha u* gamma        x -> alpha [u+] gamma
  x -> alpha u+ gamma        x -> alpha Y gamma, where y -> u | y u
  x -> alpha [beta] gamma    x -> alpha gamma | alpha (beta) gamma
  x -> alpha (beta) gamma    x -> alpha y gamma, where y -> beta
This should suffice -- I'm too tired too solve this for you. :-)

  Hans Aberg