So my amended feature request:
Create class BinaryRelation (or maybe it should be called
FiniteBinaryRelation). For this class define union, intersection,
complement, and other set operations (may we make it a subclass of some
"set" class?) and composition of relations. It should be implemented
efficiently.
In Poset class add methods like .strict_relation() and
.nonstrict_relation() to convert it to BinaryRelation. (Implicit type
conversion would be indeterminate, because it may be either strict or
nonstrict.)
Also define functions or methods for the opposite conversion (they may
throw exceptions if the relation is not an order).
I have asked for a trac account to submit my feature request, but I
received the reply:
>There is no need of trac accout for feature requests. Trac account are
>only needed to submit source code to SageMath.
So I cannot store my feature request for the Sage authors to keep track
it until the request will be accomplished. It is in my opinion bad. I
have submitted it only to sage-devel mailing list, where it may be
easily forgotten and lost. Please make it possible to store the request
in the tracker, so that the authors would have it handy as a ToDo task.
On Fri, 2018-01-12 at 00:44 +0100, Vincent Delecroix wrote:
> Thanks for your interest in Sage.
>
> As you can see at the end of the wikipedia page, this is just a
> matrix
> product followed by a truncation. And this easily done in Sage.
> Though
> one might want a more efficient way than computing a product over Z
> to
> get a {0,1}-matrix.
>
> On 12/01/2018 00:00, Victor Porton wrote:
> > Composition of binary relations is defined at
> > https://en.wikipedia.org/wiki/Composition_of_relations
> >
> > It seems that Sage does not provide a function to compose two
> > finite binary
> > relations. Please add it.
> >
> > Also note that posets (and other) are special cases of binary
> > relations. So
> > please make Poset (and other relevant classes describing a binary
> > relation)
> > a subclass of new class BinaryRelation.
> >
> > Agree? (I am a very new Sage user and may be wrong.)
> >
>
>
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