#8276: Make the one(), identity_matrix() and zero_matrix() cached and immutable.
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Reporter: hivert | Owner: hivert
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.3.3
Component: linear algebra | Keywords: One Zero mutable.
Author: Florent Hivert | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by rossk):
* keywords: One mutable. => One Zero mutable.
Comment:
I just have have a query now that Im looking at the ticket that someone
may care to answer.
I appreciate there may be implementation issues that differentiate the
different constructs i.e. M().zero() vs M(0) etc. But from a language
point of view (i.e. not considering constructions vs coercions), why are
the different matrices below treated differently i.e. why arent they all
immutable)? Im just thinking that, for example, M().zero() and
M().zero_matrix() and M(0) etc each return a zero matrix that cant be
changed (either theres an error if its immutable or the assignment is
ignored). So shouldnt they all be immutable? And why is there a variation
in the mutability between the zero and identity matrices. (Apologies if
there's something obvious I missed)
{{{
sage: MM(0).is_mutable()
True
sage: MM.zero_matrix().is_mutable()
False
sage: MM.zero().is_mutable()
True
sage: MM(1).is_mutable()
True
sage: MM.identity_matrix().is_mutable()
False
sage: MM.one().is_mutable()
False
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8276#comment:16>
Sage <http://www.sagemath.org>
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