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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] How to squeeze in place a vector matrix
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Wed, 25 Aug 2010 10:18:30 -0400
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2010/8/25 Bastien ROUCARIES <roucaries.bastien@xxxxxxxxx>:
> Hi,
>
> I want to squeeze some line and column of matrix in place, in order to
> remove the null space.
>
> How can I do that?
>
> I have tryied block(i,j,k,l).eval() but i think it is suboptimal
Ah, I see, trying to avoid aliasing issues.
In fact, in assignments, we are always traversing matrices
left-to-right and top-to-bottom.
So you can remove the eval() if you are a little careful. For example,
this works:
matrix.block(i,j,k,l) = matrix.block(i+1,j,k,l); // squeeze row i
Of course this is relying on undocumented behavior; but I really don't
see why we'd ever change this.
Benoit
>
> Bastien
>
>
>