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Ublas :

From: Russ (c.r.coggrave_at_[hidden])
Date: 2006-04-24 10:38:03

Gunter Winkler <guwi17 <at>> writes:

> On Monday 24 April 2006 16:05, Russ wrote:
> > However, now I think of it in terms of functors, if we consider the
> > situation where r1 and r2 ARE known at compile time then I can probably
> > reuse vector_binary<E1,E2,F> using a fuctor F that takes four arguments.
> > This might be easier to implement and get going, but not as general. I
> > think I should try and get this working before tackling the more general
> > case above.
> Yes, this sound very reasonable. You want to combine two vectors, so you have
> to use vector_binary and put all additional information into the functor F.

I think I am confusing myself now. Giving this a little more thought I realise
that I have ALREADY implemented the senario you described above. At the start of
this thread I mentioned that I had developed the code for

V3 = lt( V1, V2 )
V3[i] = (V1[i] < V2[i])
and the value_type for V3 is vector_expression<bool>

This is implemented in terms of a vector_binary and a functor. I can confirm
that this approach works :)

So now the next step. How to implement it for the case when r1 and r2 are not
known at compile time. At compile time, only the type of r1 and type of r2 are
known. In this case, we need to implement vector_quad_relop, which is where the
code I attached in my original message comes in.

vector_quad_relop started out as vector_binary, with some hacking around to
support 4 arguments. However, I have obviously gone wrong somewhere :(