#19319: iterator over pairs on diagonals a la Cantor pairing
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Reporter: dkrenn | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.9
Component: misc | Resolution:
Keywords: | Merged in:
Authors: Daniel Krenn | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/dkrenn/product_cantor_pairing | 70185c3a13f573cf1eacbec2eb2122082e6c375f
Dependencies: | Stopgaps:
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Comment (by cheuberg):
I have an alternative implementation (pushed as
`u/cheuberg/product_cantor_pairing`):
{{{
from itertools import count
from sage.rings.infinity import infinity
A = iter(A)
B = iter(B)
max_A = infinity
max_B = infinity
cache_A = []
cache_B = []
for s in count():
if s <= max_A:
try:
cache_A.append(next(A))
except StopIteration:
max_A = s-1
if s <= max_B:
try:
cache_B.append(next(B))
except StopIteration:
max_B = s-1
if s > max_A + max_B or max_A < 0 or max_B < 0:
return
for i in range(max(0, s-max_B), min(s, max_A)+1):
yield cache_A[i], cache_B[s-i]
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/19319#comment:21>
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