But we want the alists
((a . _.0) (b . y))
and
((b . _.1) (a . x))
to unify, yielding the mgu
((a . x) (b . y))
or equivalently
((b . y) (a . x))
And we want the alists
((a . x))
and
((b . y))
to unify, yielding the same mgu as above.
So the only way I know to encode (even unnested) feature structures
using trees is to map each feature name to a globally fixed address
in a binary tree. For example if we decide globally that "a" maps
to the address (left left right) and "b" maps to the address
(left right right left) then the alist above
((a . _.0) (b . y))
can be encoded by the tree
(((_.2 . _.0) . (_.3 . (y . _.4))) . _.5)
Maybe this is what Jason has in mind? It's related to expressing
memoization as a lazy data structure.
On 2016-12-24T12:07:14-0500, Dan Friedman wrote:
> I agree with Jason, processing alists (even split alists)i standard fare.
> Nested alists might want some constraints Haven't given that observation
> much thought.
>
> On Sat, Dec 24, 2016 at 11:08 AM, Jason Hemann <[email protected]>
> wrote:
> > I think these can be encoded using trees, yes? (Wiki seems to also suggest
> > so, if I'm reading that correctly). I know of no implementations that
> > implement feature constraints presently, but I know those have been
> > investigated
> > in other contexts
> > <http://www.sciencedirect.com/science/article/pii/0743106694900442>.
> >
> > On Sat, Dec 24, 2016 at 8:06 AM, Amirouche Boubekki <
> > [email protected]> wrote:
> >
> >> Did anyone implement minikanren for feature structure
> >> <https://en.wikipedia.org/wiki/Feature_structure>?
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