Haskell Matrix Library...

Henning Thielemann lemming at henning-thielemann.de
Thu Jun 9 08:16:17 EDT 2005

On Thu, 9 Jun 2005, Keean Schupke wrote:

> Henning Thielemann wrote:
> >MatLab must provide these automatisms because it doesn't have proper
> >higher functions. I think the Haskell way is to provide a 'map' for
> >matrices. Otherwise the question is: What is the most natural 'exp' on
> >matrices? The elementwise application of 'exp' to each element or the
> >matrix exponentation?
> >
> MatLab has "exp" which works element wise and "expm" which does the
> matrix-exponentation.

This would be the worsed possible mix - just in the spirit of MatLab. :-)
With (*) meaning a matrix multiplication and 'exp' meaning elementwise
exponentation, the exponential law
  exp (x+y) = exp x * exp y
 does not hold. For elementwise (*) operation it would hold and for 'exp'
as matrix exponentation it would hold at least for matrices x and y which
are diagonalisable by the same similarity transform.

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