[Numpy-discussion] Fix to #789 maybe not right.

[Charles R Harris]

On Wed, May 21, 2008 at 8:56 PM, David Cournapeau <
david at ar.media.kyoto-u.ac.jp> wrote:

> Charles R Harris wrote:
> > David,
> >
> > I'm not sure that fix is completely correct. The out keyword is funny
> > and I'm not what the specs are supposed to be, but generally the
> > output is cast rather than an error raised.
>
> I think the out argument is one of this thing which is rather a mess
> right now in numpy. The functions which accept it do not always mention
> it, and as you say, there are various different behaviour.
>
> What are the uses of the out argument ? The obvious one is saving
> memory, but are there others ? Automatic casting would break the memory
> saving.
>

I've been contemplating this and I think you are right. The out parameter is
for those special bits that need efficiency and should be as simple as
possible. That means: same type and shape as the normal output, no appeal.
This is especially so as a reference to the output is what the function
returns when out is present and the return type should not depend on the
type of the out parameter.

Chuck
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