#17216: Poset / LatticePoset: [meet|join]matrix algorithm
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.4
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: Jori Mäntysalo | Reviewers: Nathann Cohen
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/poset___latticeposet___meet_join_matrix_algorithm|
391c03bcc290824c78f165d1623baaf1d921734d
Dependencies: | Stopgaps:
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Comment (by tscrim):
Replying to [comment:21 jmantysalo]:
> Rollback done, `for` moved to other line.
Thanks.
> Is it so that function on "real" class overrides function with same name
in category? If so, then in principle there could be `meet_matrix()`
defined on category --- it would loop over elements and construct a
matrix. Basic implementation of lattice would only have `meet()`, but
better on could have it's own and better `meet_matrix()`(?) This is
basically what could be done in good old C++.
Yes, that's correct. Such a method would be a good benefit, although it
might be good for it to also be an enumerated set. However a lattice
morphism is stronger than a poset morphism, in that we must also have `f(a
^ b) = f(a) ^ f(b)` and similarly for joins. See
http://en.wikipedia.org/wiki/Lattice_(order). So for two lattices `L,P`,
we have `Hom(L, P) <= Hom(L, P, category=Posets())` (the first one is the
category of `Lattices`).
> Anyways, this is now ready for review. Another thing is making
documentation better. There is simply no point to make user to look
different places for `is_meet_semilattice()` and `is_lattice()`.
How most (from my experience) people get documentation is interactively
(i.e. `P.is_lattice?`), so it doesn't make a difference where the method
is located.
--
Ticket URL: <http://trac.sagemath.org/ticket/17216#comment:22>
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