|Re: [eigen] problem with operator() in development branch|
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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] problem with operator() in development branch
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Tue, 1 Jun 2010 21:09:56 -0400
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2010/6/1 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
> On Tue, Jun 1, 2010 at 2:55 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
>> oh, right ! Don't know why I didn't remember about that. By the way,
>> are you planning to allow 1x1 to scalar conversion ? I'm rather
>> favorable to that. There recently was an unanswered forum post about
>> doing that.
> ok I've a working version of that:
> Matrix<float,1,1> mat;
> mat = 1;
> float x = mat + 1
> but there is a quite big downside:
> mat * 2
> does not compile anymore because there is an ambiguity which has to be
> resolved by doing either:
> mat * Scalar(2);
> mat * 2.f;
> Scalar(mat) * 2;
> Maybe the worst thing is that such an ambiguity will show up for 1x1 objects
> only... so think about general template code which compile fine for all
> objects except 1x1. Since the later ones are likely not be well tested.....
Hm, good you thought about that, this is indeed not very rejoicing!
> I'm tempted to postpone this feature and/or enable this conversion for inner
> products only which are less likely to trigger such issues.
..... and moreover, is probably the most frequent use case. Yes, I'd
like that very much!
> Also for other
> use cases there is the class Array which is supposed to be explicitly fully
> compatible with scalars.