#12453: Refactor integer vectors using ClonableIntArray Cython data structure
-------------------------------------+-------------------------------------
Reporter: nborie | Owner: nborie
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.2
Component: combinatorics | Resolution:
Keywords: Integer, vectors, | Merged in:
cython, clone, Cernay2012 | Reviewers:
Authors: Travis Scrimshaw | Work issues:
Report Upstream: N/A | Commit:
Branch: | 3008ee6a34c023370071bfe1fb324f2b479462ed
public/refactor_integer_vectors-12453| Stopgaps:
Dependencies: #10193 #14101 |
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Comment (by ncohen):
> By your convention, I mean revlex.
Me and quite a lot of people (wikipedia, dictionaries, phone books,
Python) seem to agree on what a lexicographic ordering is `:-P`
It looks like `IntegerVector` returns them in decreasing lexicographic
order, so I guess that's what you call "revlex" (sorry I always mix colex
and revlex).
What about computing the complement of x ? In Python it wastes a lot of
time, but the algorithm works.... `:-P`
{{{
def integervectors(n,k):
L = n+k-1
for x in combinations(range(L),L-(k-1)):
x_complement = []
j = 0
for i in range(L):
if x[j] == i:
if j < L-(k-1)-1:
j += 1
continue
else:
x_complement.append(i)
x = x_complement
l = [x[i] - x[i-1]-1 for i in range(1,k-1)]
l.insert(0,x[0])
l.append(L-x[-1]-1)
yield l
sage: list(integervectors(5,5)) == [list(map(int,x)) for x in
IntegerVectors(5,5)]
True
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/12453#comment:21>
Sage <http://www.sagemath.org>
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