PM-Question

[Dan Bothell]

--On Thursday, July 25, 2002 3:34 PM +0200 Wolfgang Schoppek 
<Wolfgang.Schoppek at uni-bayreuth.de> wrote:

> Is there a possibility to include a test for "emptyness" of a buffer
> in a production rule?
> Something like
>
> (p ...
>    =goal>
>      ...
>    =visual-location>
>       is-empty
> ==>
> ...
> )
>
> ?

There isn't an explicit test for an empty buffer at this point - that's one of 
those issues that has yet to be resolved.  For the =visual buffer the empty 
case is indistinguishable from the isa error case, so you can use that there, 
but for the =visual-location buffer that doesn't work.  If you really need it 
you could use a !eval! hack to test it:

(p hacked-empty-test
!eval! (null (car (buffers visual-location)))
==>
)

Dan