[Numpy-discussion] Do we want scalar casting to behave as it does at the moment?

Dag Sverre Seljebotn d.s.seljebotn@astro.uio...
Tue Jan 8 15:37:51 CST 2013

On 01/08/2013 10:32 PM, Dag Sverre Seljebotn wrote:
> On 01/08/2013 06:20 PM, Andrew Collette wrote:
>> Hi,
>>> I think you are voting strongly for the current casting rules, because
>>> they make it less obvious to the user that scalars are different from
>>> arrays.
>> Maybe this is the source of my confusion... why should scalars be
>> different from arrays?  They should follow the same rules, as closely
> Scalars (as in, Python float/int) are inherently different because the
> user didn't specify a dtype.
> For an array, there was always *some* point where the user chose,
> explicitly or implicitly, a dtype.
>> as possible.  If a scalar value would fit in an int16, why not add it
>> using the rules for an int16 array?
> So you are saying that, for an array x, you want
> x + random.randint(100000)
> to produce an array with a random dtype?
> So that after carefully testing that your code works, suddenly a
> different draw (or user input, or whatever) causes a different set of
> dtypes to ripple through your entire program?
> To me this is something that must be avoided at all costs. It's hard
> enough to reason about the code one writes without throwing in complete
> randomness (by which I mean, types determined by values).

Oh, sorry, given that this is indeed the present behaviour, this just 
sounds silly. I should have said it's something I dislike about the 
present behaviour then.

Dag Sverre

> Dag Sverre
>>> Returning to the question of 1.5 behavior vs the error - I think you
>>> are saying you prefer the 1.5 silent-but-deadly approach to the error,
>>> but I think I still haven't grasped why.  Maybe someone else can
>>> explain it?  The holiday has not been good to my brain.
>> In a strict choice between 1.5-behavior and errors, I'm not sure which
>> one I would pick.  I don't think either is particularly useful.  Of
>> course, other members of the community would likely have a different
>> view, especially those who got used to the 1.5 behavior.
>> Andrew
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