export Base.LinAlg.chksquare

[tpapp]

Rationale: checking that a matrix is square is a pretty common operation. While chksquare is a minor utility function, it is well-designed, useful, and allows standard error reporting. Without a common function, libraries end up implementing their own solutions or explicitly spell out something like

n, m = size(A)
if n != m
    throw(ArgumentError("matrix is not square"))

or one of the countless variations. Standardizing this outside Base.LinAlg would be useful.

[andreasnoack]

I gree that it would be a useful function to expot, but I don't like the chk abbreviation though. Maybe rename to checksquare, write documentation and export in a PR would be the way to proceed.

[tpapp]

I will try submitting a PR, as I mean to learn the workflow anyway and such a minor change would be a good place to start.

[tkelman]

This could be used elsewhere without exporting it, just by qualifying it with the module name. I'd be in favor of renaming and documenting it, but not exporting such a trivial thing.

[KristofferC]

If the name is changed it should be deprecated even though it is a non exported function. It is likely used in many places out of Base.

[StefanKarpinski]

How about renaming it to checksqr?

[tpapp]

How would I note in the documentation that it is not exported? Is there a convention, eg using the full form Base.LinAlg.checksquare?

[tkelman]

Or just LinAlg.checksquare since the LinAlg module is exported. That's the convention used for Profile and a few other places, yes.

[andreasnoack]

See e.g. https://github.com/JuliaLang/julia/blob/10e8b52f40a6ec42217b7c632920d9651b580528/base/linalg/qr.jl#L141-L162

[jiahao]

To clarify, chksquare does more than just check if the matrix is square. If it is square, it also returns the dimension of the matrix, which is an extremely common thing to do. Perhaps we can come up with a name that reflects its return value too.

[tpapp]

What about checked_square_size? A bit long, but reflects the fact that it returns a dimension, and the argument has been checked to be square.

[andreasnoack]

I think checksquare is fine if we document the behavior and give an example.

[StefanKarpinski]

+1 for checksquare.

[tpapp]

I just submitted PR JuliaLang/julia#14601, which should close this. Thanks for all the help.