On Sat, Feb 12, 2005 at 03:28:15AM +0800, Autrijus Tang wrote:
> On Fri, Feb 11, 2005 at 09:42:06AM +0000, Thomas Yandell wrote:
> > Is there another operator that takes the intersection of two
> > junctions, such that any(2,3,4,5) *some op* any(4,5,6,7) would result
> > in any(4,5)?
>
> Yes. In Pugs 6.0.3 (released one minute ago), that operator is
> simply called "&":
>
> % ./pugs -e "(any(2,3,4,5) & any(4,5,6,7)).perl"
> ((2 | 3 | 4 | 5 | 6 | 7))
>
> That is, the "&" builder now automagically collapses nested
> junctions under it. I intend to fill in the rest of the collapse
> logic tomorrow, after some feedback from the list.
This collapse is probably wrong. In particular,
any($a, $b) & any($b, $c)
is not the same as
any($a, $b, $c)
To see this, set $a=1, $b=0, $c=0:
any($a, $b) & any($b, $c)
-> any(1,0) & any(0,0)
-> false
any($a, $b, $c)
-> any(1, 0, 0)
-> true
> Consider:
>
> all( one(1, 2), one(2, 3) )
>
> Should it be collapsed into:
>
> any( one(1, 3), 2 )
>
> so that "2" now only occurs once? Is it sane?
No, it's wrong.
all( one(1, 2), one(2, 3) ) # false
any( one(1, 3), 2) # true
There might be some junctions that can be "collapsed", but these
aren't examples of them.
Pm
