Matrix division fails on 0.10 about core.matrix

[mikera]

Confirmed - seems to be a big in NDArray assuming that the second argument is a scalar number (when it could be any shape-compatible array)

It works fine for regular persistent vectors:

(def X [[1 2] [3 4]])
(div X X)
=> [[1 1] [1 1]]

@si14 are you able to take a look and fix this one? I get the suspicion that it may affect some other functions in NDArray too

[tgoossens]

Its probably just me. But as far as I know the matrix division is not defined like that. Because matrix multiplication is not commutative.

There is no way to know whether A/B
means B^-1 * A or A * B^-1 unless a convention is made which I would strongly dislike.

[mikera]

@tgoossens - I agree with you that matrices can't be easily divided for the reason that you describe.

However we're talking about a slightly different operation here - div is for element-wise division. So I think it is reasonably well defined as "elements of a divided by corresponding elements of b"
(with broadcasting as necessary to make the array sizes conformant).

[tgoossens]

My bad. Should have read the documentation better.

[mikera]

This is fixed I think by this commit:
e5c7d0a