add zero_matrix constructor.

[ncalexan]

This adds the zero_matrix convenience constructor, just like identity_matrix.

CC: @ncalexan

Component: linear algebra

Keywords: zero matrix identity one

Issue created by migration from https://trac.sagemath.org/ticket/2299

[malb]

comment:1

Attachment: 2299-ncalexan-zero-matrix-1.patch.gz

You replaced "n x n" by "$n \times n$" which reads nicer if typesetted. However, it is harder to comprehend from the command line (foo?).

I am not sure that we need identity_matrix and zero_matrix (i.e. the functional versions of MS(0) and MS(1)) but that is a matter of taste.

[ncalexan]

comment:2

I really want identity_matrix and zero_matrix because I often don't want to name the matrix space in advance. MS(0) requires me to create said space first.

As for latex in docstrings... I don't care either way. I think it should be latex but I parse simple latex from tex without trouble.

[williamstein]

comment:3

Just a quick remark. You can make a zero matrix using the matrix function:

sage: matrix(ZZ, 2,3)
[0 0 0]
[0 0 0]

I don't think that's a good reason not to add zero_matrix and identity_matrix
functions though, both of which I would like to have too.

[ncalexan]

comment:4

I think zero_ and identity_ declare programmer intent nicely. Will someone say positive or negative and this either goes to the bit-bucket or gets applied?

[williamstein]

comment:5

REFEREE REPORT:

I definitely think these functions should go in, but with TWO caveats.

1. I think the zero_matrix should have an option to be nonsquare though. Please post another patch that adds that, so, e.g.,

sage: zero_matrix(ZZ, 2,3)
[0 0 0]
[0 0 0]

works.

2. There should be a sparse option for both zero_matrix and
   identity_matrix.

sage: zero_matrix(ZZ, 2,3, sparse=True).parent()
Full MatrixSpace of 2 by 3 sparse matrices over Integer Ring

-- William

[ncalexan]

Attachment: 2299-ncalexan-zero-matrix-2.patch.gz

[ncalexan]

comment:7

2299-ncalexan-zero-matrix-2.patch should apply without the previous patch, and should address the referee's comments.

I generated this patch using hg diff between two revisions, not hg export. Let me know if it's not okay.

[mwhansen]

comment:8

Works for me in 2.10.3.alpha0. Note that only the last patch should be apply and that it is a "raw" patch.

[mwhansen]

Attachment: 2299.patch.gz

[mwhansen]

comment:9

I just realized this conflicts with #874. #874 should be applied first, and then 2299.patch should be applied.

[sagetrac-mabshoff]

comment:10

Merged 2299.patch in Sage 2.10.3.rc0