Yes. On Jun 13, 1:22 am, Jason Grout <jason-s...@creativetrax.com> wrote: > A few months ago, #8276 made the MatrixSpace identity_matrix and > zero_matrix methods return immutable matrices, following a discussion on > sage-devel. A consequence of this (unintended, I hope!) was that the > top-level identity_matrix and zero_matrix methods now return immutable > matrices. This now causes several problems: > > 1. It breaks existing code > > 2. It makes the top-level matrix constructors inconsistent (every other > constructor in matrix/constructors.py returns a mutable matrix). > > 3. It breaks consistency with the 4 M's, which all return mutable > matrices from the top-level identity matrix constructor. > > 4. It requires someone that just wants to create a zero/identity matrix > and then modify it to either do copy(identity_matrix(...)) or learn > about MatrixSpace and do something like MatrixSpace(...)(1). Both of > these options require needless annoyances, especially for someone that > is just learning Sage or familiar with the 4 M's. > > Note that the discussion for #8276 did not touch the top-level > constructors (it dealt with the matrix space methods), so this is a > different issue that brought up in #8276. The changes in #8276 to the > matrix space methods will still hold. Effectively, this proposal is > about changing the top-level identity_matrix function to return > MatrixSpace(...)(1) (a mutable copy) instead of MatrixSpace(...).one(). > > So, please vote: > > [ ] Yes, make top-level identity_matrix and zero_matrix functions return > mutable matrices again, i.e., this code will work, and will not have the > bugs #8276 pointed out: > > sage: M=identity_matrix(3) > sage: M[0,0]=3 > > [ ] No, keep the changed behavior (this option entails requiring users > to do something like copy(identity_matrix(...)) or MatrixSpace(...)(1) > to construct a mutable identity matrix, like so: > > sage: M=copy(identity_matrix(3)) > sage: M[0,0]=3 > > The patch at > > http://trac.sagemath.org/sage_trac/ticket/9212 > > implements the "yes" vote, and is ready for review (if the ticket is > reopened as a result of this vote.) > > Thanks, > > Jason
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