#7947: iteration error in QuadraticForm.vectors_by_length()
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Reporter: tornaria | Owner: tornaria
Type: defect | Status: positive_review
Priority: major | Milestone: sage-4.3.2
Component: quadratic forms | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by jonhanke):
* status: needs_review => positive_review
Comment:
This is a subtle bug which arises because negative numbers are created
when the round and ceil functions cause upper and lower bounds to
inadvertently move past each other. The patch discards partial vectors
where this happens by incrementing (successively if necessary) to the next
possible partial vector, which is the correct thing to do. Also the patch
omits using a condition (i<n-1) as in Comment 3a slightly below the patch,
which is ok because zero will always be an allowed value for the (n-1)st
entry since that first allowed interval is not shifted at all.
The patch looks good. =)
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7947#comment:2>
Sage <http://www.sagemath.org>
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