#18944: Posets: maximal_chains() partial-option broken
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Reporter: jmantysalo | Owner:
Type: defect | Status: needs_info
Priority: major | Milestone: sage-6.9
Component: combinatorics | Resolution:
Keywords: posets | Merged in:
Authors: Jori Mäntysalo | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jmantysalo/maximal_chains | e6a4ae2b1f7f887b58a49af5c1607640c7821dde
Dependencies: | Stopgaps:
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Changes (by jmantysalo):
* status: needs_work => needs_info
Comment:
Replying to [comment:9 tscrim]:
> I agree with Kevin, bad input is bad input and you should not expect
correct behavior. So there is no counterexample to the function working as
documented, but we should raise an error when not given a saturated chain.
Should `partial` be a saturated chain starting from some minimal element?
Should it be ordered?
And why it should be saturated? If `a`, `b` and `c` are comparable, then
`maximal_chains(partial=[a,b,c])` can be well defined: return every
maximal chain that contains all three elements. On the other hand,
`chains()` have `exclude`-option, not `include`. (Of course there are FOUR
ways to have argument like this: include some element, include all
elements, do not include all elements, do not include any of elements.)
I am quite sure that this function has been made just as a helper
function, without thinking someone to use `partial` directly.
--
Ticket URL: <http://trac.sagemath.org/ticket/18944#comment:10>
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