Re: looking for a predicate hierarchy


Laurent Deniau wrote:
I am looking for a library (of an OO language) which uses a hierarchy of
classes for predicate (type) dispatch in the context of multimethod. Ce
concept is already well know and developed in the literature, but
languages which support multimethods and metaclasses are not so common.
Therefore, I have some difficulty to find such 'standard' use of class
as predicates. The papers usually use hierarchies inspired from specific
taxonomy (e.g. animals) which are not general enough to be useful.

For the moment in my lib I have (<- means 'inherits from'):

Predicate (root class)
<- Nil
<- TrueFalse
<- True
<- False
<- Ordered
<- Lesser
<- Equal
<- Greater

But there is a lot of other possible predicates (not all useful):

Next, Previous
Forward, Backward
Open, Close
Front, Rear
Bottom, Top
Before, After
Up, Down
Even, Odd
Left, Right
North, South, Est, West

etc...

and selecting the predicates general enough (aliases and user defined
predicates are always possible as extension) is somehow a problem of
experience. BTW, the hierarchy stigmatize the possible logical
combinations of the predicates (not, and, or) and strengthens the
importance of its design (e.g. TrueFalse != Boolean).

Has somebody already seen such hierarchy? Links and references would be
really appreciated. Thanks.

What do you mean by "predicate"? Is it logical concept? Then we can
talk about relations in the database theory sence, both finite and
infinite. Relations do form a lattice, so you work out tthis idea into
extracting a "hierarchy" out of the lattice. But is this really what
you want to do?

.

Relevant Pages

  • looking for a predicate hierarchy
    ... I am looking for a library (of an OO language) which uses a hierarchy of classes for predicate dispatch in the context of multimethod. ... I have some difficulty to find such 'standard' use of class as predicates. ...
    (comp.object)
  • Re: looking for a predicate hierarchy
    ... languages which support multimethods and metaclasses are not so common. ... But there is a lot of other possible predicates: ... the hierarchy stigmatize the possible logical ... The set of all possible binary relations defined on ...
    (comp.object)
Loading