#17002: Hasse diagrams: Trivial simplification for three functions
-------------------------------------+-------------------------------------
Reporter: jmantysalo | Owner:
Type: enhancement | Status: needs_review
Priority: trivial | Milestone: sage-6.4
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/poset_is_chain__trivial_simplification|
b8b24e0a104864c62c24831cc3d7d366dbb98156
Dependencies: | Stopgaps:
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Changes (by jmantysalo):
* cc: ncohen (added)
* commit: => b8b24e0a104864c62c24831cc3d7d366dbb98156
* status: new => needs_review
Old description:
> A poset is chain if |V|-1=|E|, no vertex has out-degree >1 and no vertex
> has in-degree >1. Hence after #16984 code block
>
> {{{
> seen_0 = False
> for d in self.out_degree():
> if d == 1:
> pass
> elif d == 0:
> if seen_0:
> return False
> seen_0 = True
> else:
> return False
> }}}
>
> can be shortened to be just
>
> {{{
> if any(d>1 for d in self.out_degree()):
> return False
> }}}
New description:
A poset is chain if |V|-1=|E|, no vertex has out-degree >1 and no vertex
has in-degree >1. Hence after #16984 it can be further simplified. Also
`maximal_elements` and `minimal_elements` can use just `sources` and
`sinks`.
--
Comment:
New commits:
||[http://git.sagemath.org/sage.git/commit/?id=b8b24e0a104864c62c24831cc3d7d366dbb98156
b8b24e0]||{{{Simplification of is_chain, maximal_elements and
minimal_elements.}}}||
--
Ticket URL: <http://trac.sagemath.org/ticket/17002#comment:2>
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