| Re: [eigen] Matrix - Scalar CwiseUnaryOps |
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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Matrix - Scalar CwiseUnaryOps
- From: Hauke Heibel <hauke.heibel@xxxxxxxxxxxxxx>
- Date: Wed, 4 May 2011 15:00:29 +0200
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Ok. fine enough. I just thought we could be a bit less strict here but
I understand your reasoning.
On Wed, May 4, 2011 at 2:55 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> Yes, the ambiguity is between interpreting a+M as
> 1) aE+M where E is the matrix all of whose coefficients are 1; this
> is what we do for arrays; or
> 2) aI + M where I is the identity matrix; this is definitely what
> mathematicians mean by a+M whenever they use that notation. This is
> required if you want basic matrix arithmetic rules to be self
> consistent, e.g. distributivity: (a+M)*N = aN + M*N
>
> This ambiguity is the primary reason why we leave this undefined in Eigen..
>
> Benoit
>
> 2011/5/4 Thomas Capricelli <orzel@xxxxxxxxxxxxxxx>:
>>
>> Hi,
>>
>> From a mathematical point of view a.M is defined but a+M is not...
>> (a=scalar, M=Matrix).
>>
>> my 2 cents..
>>
>> Thomas
>>
>> --
>>
>> Thomas Capricelli <orzel@xxxxxxxxxxxxxxx>
>>
>> http://www.freehackers.org/thomas
>>
>> On Wednesday 04 May 2011 11:39:13 Hauke Heibel wrote:
>>
>>> Hi,
>>
>>>
>>
>>> I know that we have the array functionality for those operations but I
>>
>>> wonder whether we should enable +/- operations between matrices and
>>
>>> scalars.
>>
>>>
>>
>>> We already have * and / and thus I think it might make sense. It's
>>
>>> just for convenience and I have met quite a few occasions where this
>>
>>> feature would lead to shorter code. What do you think?
>>
>>>
>>
>>> - Hauke
>>
>>>
>>
>>>
>>
>>>
>>
>
>
>