[Numpy-discussion] matrix default to column vector?

Robert Kern robert.kern@gmail....
Sun Jun 7 19:52:28 CDT 2009


On Sun, Jun 7, 2009 at 18:44, Eric Firing<efiring@hawaii.edu> wrote:
> Robert Kern wrote:
>> On Sun, Jun 7, 2009 at 04:44, Olivier Verdier <zelbier@gmail.com> wrote:
>>> Yes, I found the thread you are referring
>>> to: http://mail.python.org/pipermail/python-dev/2008-July/081554.html
>>> However, since A*B*C exists for matrices and actually computes (A*B)*C, why
>>> not do the same with dot? I.e. why not decide that dot(A,B,C) does what
>>> would A*B*C do, i.e., dot(dot(A,B),C)?
>>> The performance and precision problems are the responsability of the user,
>>> just as with the formula A*B*C.
>>
>> I'm happy to make the user responsible for performance and precision
>> problems if he has the tools to handle them. The operator gives the
>> user the easy ability to decide the precedence with parentheses. The
>> function does not.
>>
>
> The function could, with suitable parsing of the argument(s):
>
> (A*B)*C => dot( ((A,B),C) )     or  dot( (A,B), C )
> A*(B*C) => dot( (A, (B,C)) )    or  dot(  A, (B,C) )
>
> Effectively, the comma is becoming the operator.

Already discussed on the old thread.

-- 
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


More information about the Numpy-discussion mailing list