#17053: Add function for direct sum of posets
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-wishlist
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by jmantysalo):
Function could then be something like
{{{
def direct_sum(self, other, relabel=None):
if not hasattr(other, 'hasse_diagram'):
raise ValueError('The input is not a finite poset.')
if relabel == None:
elements=self.list()+other.list()
if len(elements) != len(set(elements)):
raise ValueError("Posets contain equal elements. Try
relabel='pairs' or relabel='linear'.")
return Poset(self.hasse_diagram().union(other.hasse_diagram()))
if relabel == 'pairs':
return
Poset(self.hasse_diagram().disjoint_union(other.hasse_diagram()))
if relabel == 'linear':
return
Poset(self._hasse_diagram.disjoint_union(other.hasse_diagram(),
verbose_relabel=False))
}}}
1) Why I must say `other.hasse_diagram()` on last line,
`other._hasse_diagram` should work. Again some copy-immutable -thing?
2) What should be the name of parameter and values for it?
`verbose_relabel` to be consistent with graphs? Default value for it?
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Ticket URL: <http://trac.sagemath.org/ticket/17053#comment:6>
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