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Re: How to make Bison disregard tokens?

From: Edsko de Vries
Subject: Re: How to make Bison disregard tokens?
Date: Fri, 2 Mar 2007 12:01:42 +0000
User-agent: Mutt/1.5.9i

On Fri, Mar 02, 2007 at 12:55:29PM +0100, address@hidden wrote:
> On Friday 02 March 2007 12:30, Edsko de Vries wrote:
> > Hi,
> >
> > Is there any way I can make Bison ignore tokens when it can't deal with
> > them? I'll try to explain. For every completely blank line in the input,
> > my leexer generates a NOP token. In some situations the parser can deal
> > with this NOP token; in others it can't. 
> If you need to ignore the blank lines, just make sure your scanner doesnt 
> return a token to the parser.

Well, no, that's the point. Blank lines should be recorded as NOPs where
possible, so that we know where they are and unparse them. For example,
if the user writes

$a = 5;
$b = 6;


(I'm working on phc, which works on PHP), we want to unparse it like
that, and not like

$a = 5;
$b = 6;

By inserting the NOP at the blank line, we can avoid this.


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