Prevent creation of code with length 0

[fdosso48]

AbstractLinearCode class allows construction of code with length 0. The goal of this ticket is to prevent this.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​c144ddf

Adds an exception that prevent creation of code with length 0

[erousseau]

Hi,

I just changed the indentation in the file, that didn't fit with Sage conventions. I think it's fine but it needs review.

Best, Édouard

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New commits:

​6075248	Fixed a bug related to subdivide method
​482ae02	added doctest
​10460b4	Improves a little the 'subdivide' method documentation
​ad3d72a	Merge branch 'u/fdosso48/code_with_length_0' of trac.sagemath.org:sage into code_with_length0
​25c0758	I removed some spaces to fit with Sage conventions.

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

[erousseau]

Sorry, I did an error, I just fixed my error, not the original fix I did, you can see the diff in 25c0758 just above, just ignore the rest of it...

Best, Édouard

[dlucas]

Hello Édouard,

As you just fixed an error related to the indentation level, I think it's fine if you complete the review process yourself. It's not a fundamental change, so it's fine :)

David

[erousseau]

Hi Fangan,

It might be good to add a doctest that explains that the length 0 is not available anymore, and to mention this ticket !

Best, Édouard

[fdosso48]

Hi,

I agree, it is a good idea.

Best, hoping you are doing it :)

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​8ddca4a

I added a doctest testing the new exception.

[erousseau]

I added a doctest, just as I suggested above. It's open for review.

Best, Édouard

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​d03f2de

Fixed a typo.

[bruno]

Two doctests are broken in src/sage/coding/encoder.py (lines 204 & 207). Actually, these doctests are specifically for the behavior of encoders with length equal to 0!

[erousseau]

Replying to bruno:

Two doctests are broken in src/sage/coding/encoder.py (lines 204 & 207). Actually, these doctests are specifically for the behavior of encoders with length equal to 0!

You are totally right, should I just remove those doctests then ?

[bruno]

Replying to erousseau:

Replying to bruno:

Two doctests are broken in src/sage/coding/encoder.py (lines 204 & 207). Actually, these doctests are specifically for the behavior of encoders with length equal to 0!

You are totally right, should I just remove those doctests then ?

That may be the right thing to do yes. You may replace the whole block of doctests by something like

Note that since ticket :trac:`21326`, codes cannot be of length zero::

    sage: G = Matrix(GF(17),[])
    sage: C = LinearCode(G)
    Traceback (most recent call last):
    ...
    ValueError: length must be a non-zero positive integer

My only hesitation is whether the presence of these doctests in src/sage/coding/encoder.py are a indication that codes of length zero may be useful to have. I really have no idea what this should be, but you may asked David or Johan just to be sure.

[fdosso48]

My only hesitation is whether the presence of these doctests in src/sage/coding/encoder.py are a indication that codes of length zero may be useful to have. I really have no idea what this should be, but you may asked David or Johan just to be sure.

Actually, I asked David and Johan before doing this method. So, it's ok, the block of doctests can be replaced by what you propose.

[bruno]

Replying to fdosso48:

My only hesitation is whether the presence of these doctests in src/sage/coding/encoder.py are a indication that codes of length zero may be useful to have. I really have no idea what this should be, but you may asked David or Johan just to be sure.

Actually, I asked David and Johan before doing this method. So, it's ok, the block of doctests can be replaced by what you propose.

OK, I let you doing so. I guess I'll be able to positively review the ticket once this is done.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​dfc829a

I changed a doctest that was broken.

[erousseau]

I changed the doctest by the one suggested by Bruno.

Édouard

[bruno]

Everything's OK, documentation successfully builds. I add a commit to remove some trailing spaces in the two modified files.

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New commits:

​c810635

21326: Remove trailaing spaces [reviewer]