
Boost : 
From: David Abrahams (david.abrahams_at_[hidden])
Date: 20010613 19:34:08
 Original Message 
From: "Hubert HOLIN" <Hubert.Holin_at_[hidden]>
> >
> > I'm very interested. It's one of the things we'll be needing for our
work
> > here.
>
> OK, I'll dig it up. In the mean time you might be interested
> in FFTW (http://www.fftw.org/) against which I ave not tested my
> implementation but which should be good for most applications (in C).
Yes, we know about that one, thanks.
> > > > > Quadtrees and higherdimentional analogues represent another form
> > > > > of indexing fun that should not be overlooked.
> > > >
> > > > Aren't these really a completely separate application domain? We do
not
> > need
> > > > to invent a universal iteration interface.
> >
> > I would still like to know the answer...
>
> I believe that, yes, we are still in the same problem domain.
> I see this as traversing in different ways an object which can be
> viewed at times as storage, at times as an algebraic object.
I guess "quadtree" means something different to you than it does to me. I
thought it was a kind of spatial indexing system used often in 3d graphics
applications.
> > I would prefer to see sophisticated operations taking iterator
parameters
> > (possibly among others) as available, rather than building sophisticated
> > behavior into the iterators themselves.
>
> One (among many) ways to see things is to remember that the
> mathematical definition of a matrix is a function (not the
> representation of some linear or bilinear operator, that comes as a
> fringe benefit, but as a function from some subset of NxN (or greater)
> to whatever set we are considering for values).
That view corresponds well with the linear algebra concepts we've been
looking at.
> An iterator is,
> basicaly, some form of bijection from a subset of N into the set of
> indices we are interested in.
I'm not sure if that part rings true. Maybe you should clarify a bit.
> A 'behaviour' is then simply some
> function from the set of indices to itself.
Maybe you should give an example of what you've got in mind.
> >
> > OK; I have no objection to interfaces which make valarrays usable, but I
> > worry about carefully tailoring the library to use them.
> >
> > Dave
>
> They also are usefull "internally". For the final version of
> my quaternions and octonions I found practical to use them, but they
> are just some implementation detail, they are invisible to the user.
I'm convinced about valarray, now. It's basically a likely way to access
optimizations which would otherwise require platformspecific code or
nonstandard tricks.
Dave
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk