[Python-ideas] Fwd: [RFC] draft PEP: Dedicated infix operators for matrix multiplication and matrix power

[Robert Kern]

On 2014-03-26 18:59, Sturla Molden wrote:
> On 14/03/14 18:53, Guido van Rossum wrote:
>
>> - Did you consider a duck-typing (is that the word?) attribute?
>>    E.g. a*b is elementwise multiplication; a.M*b must be used for
>>    matrix multiplication.
>
> This is exactly what has been tried with the types numpy.matrix and numpy.array.

For the record, no it hasn't. The proposal here is different than the 
numpy.matrix status quo. The proposed result of `a.M*b` would be an ndarray, not 
whatever the .M type is. The .M type would not be intended to be used outside of 
a multiplication expression. It is unlikely to propagate through ones code the 
way that numpy.matrix does (at least, it would be considered a bug to let a free 
.M type loose). One could safely write their functions expecting only 
numpy.ndarrays.

While this proposal has been considered and rejected, it is not the same as 
numpy.matrix and has been rejected for different reasons.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco