ishessenberg does not check for square matrix

[wbhart]

Currently, we can only put a matrix in Hessenberg form if it is square. But we allow non-square matrices in ishessenberg. I'm just wondering if it was intentional, and whether we should return false or an exception if it is not square.

[wbhart]

Same question applies to similarity!, which applies a similarity transform. The code seems to only work for square matrices, and the docs seem to suggest we assume that. I'm wondering if there is a reason we don't test for squareness there, or whether I should just add that in.

[thofma]

I think returning false in ishessenberg sounds like a good option.

Regarding similarity!, I don't know what it is doing, but usually we don't check arguments for unsafe functions (exception is setindex!).

[wbhart]

Ok, thanks.