#20008: Implement non-recursive iterator for compositions
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Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-7.1
Component: combinatorics | Resolution:
Keywords: iterator | Merged in:
Authors: Travis Scrimshaw | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/combinat/composition_iterator-20008|
a796f0eb320c7955d2007486fefd2407a9bb7345
Dependencies: | Stopgaps:
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Comment (by tscrim):
Replying to [comment:5 darij]:
> Grammar error in doc.
>
> More importantly, though, I'm not sure I understand the algorithm. Why
does it not decrement `s` in the `s > n` case?
Actually, that case never happens unless `n < 0`. So that could be
removed.
> What is the logic behind the algorithm anyway?
The idea is to find the lex smallest composition by adding a box each
step. If we have a composition of `n`, then yield and remove the last
column and add a box to the new final column. Otherwise add a box to the
end. Hmmm....implementing it directly from that would probably be a little
cleaner since `cur` would always be a valid partition. Let me change that
now.
--
Ticket URL: <http://trac.sagemath.org/ticket/20008#comment:6>
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