🚀 go-pugleaf

>>>>> "Peter" == Peter Moylan <peter@fourier.newcastle.edu.au> writes:
In article <40bjb1$qgs@seagoon.newcastle.edu.au> peter@fourier.newcastle.edu.au (Peter Moylan) writes:

Peter> That's an interesting example, because it comes up in
Peter> connection with implementing things like the Fast Fourier
Peter> Transform.  The way it arises - I imagine that Marco already
Peter> knows this, but some other readers might not - is that at
Peter> certain points in the calculation you have to rearrange an
Peter> array such that, for all j, A[j] has to be swapped with
Peter> A[BitReverse(j)], where BitReverse(.)  is the transformation
Peter> Marco mentions above.

I would guess that BitReversal of bytes is fastest using a 256 byte
array containing the reversed bit-patterns.  BitReversals of sets
smaller than 8 bit can be done by combining the above array with * or
DIV operations.  BitReversal of larger sets can be done by combining
the above operations.

Peter> On a completely different topic: in another posting, Marco
Peter> commented on the expression "not being able to see the wood for
Peter> the trees".  Yes, this is a well-known expression in the
Peter> English language; I didn't pick it up from Dutch.  (Ik kan geen
Peter> nederlands spreken.)  If it also occurs in Dutch, then I guess
Peter> it must be a very old expression that existed in the common
Peter> ancestor of the two languages.  Can anyone tell me whether the
Peter> expression also exists in German - or, for that matter, in any
Peter> other language?

The expression exists in Norwegian (ikke se skogen for bare trær).

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