On Mon, May 11, 2015 at 2:53 PM, Alan G Isaac <alan.isaac@gmail.com> wrote:
I agree that where `@` and `dot` differ in behavior, this should be clearly documented.
I would hope that the behavior of `dot` would not change.

Even if np.dot never changes (and indeed, perhaps it should not), issuing these warnings seems like a good idea to me, once we have @ implemented with the new behavior (and the @ operator backported from Python <3.5 as a numpy function).

I expect that this warning would serve the useful purpose of reminding users writing code intended to be used on earlier versions of numpy/python that @ and np.dot don't work exactly the same way. As Nathaniel already mentioned, it is quite straightforward to implement the "outer product" behavior using the new @ behavior, so it will not be much of a hassle to update code to remove the warning.

Stephan