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[Python-Dev] PEP 465: A dedicated infix operator for matrix multiplication

Nathaniel Smith njs at pobox.com
Wed Apr 9 13:47:10 CEST 2014 
On 9 Apr 2014 12:34, "Robert Kern" <robert.kern at gmail.com> wrote:
>
> On 2014-04-09 12:12, Nick Coghlan wrote:
>>
>> On 8 April 2014 18:32, cjw <fn681 at ncf.ca> wrote:
>>>
>>> Guido,
>>>
>>> I am sorry to read this.
>>>
>>> I shall be responding more completely in a day or two.
>>>
>>> In my view, @ and @@ are completely redundant.  Both operations are
 already
>>> provided, * and **, in numpy.matrix.
>>>
>>> PEP 465 provides no clear indication as to how the standard operators
fail.
>>
>>
>> Note that numpy.matrix is specifically discussed in
>>
http://www.python.org/dev/peps/pep-0465/#rejected-alternatives-to-adding-a-new-operator
>> (it's the first rejected alternative listed).
>
>
> To be fair to Colin, the PEP asserts that the community at large would
prefer an operator to the status quo but only alludes to the reason why it
does so rather than explaining it fully. Personally, I think that's a
reasonable allocation of Nathaniel's time, but then I happen to have agreed
with the PEP's position before it was written, and I personally witnessed
all of the history myself so I don't need it repeated back to me.

It could doubtless be clearer or signposted better, but the most explicit
explanation of why the two type solution doesn't work is in the first
section, search for "network effects".

-n
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