[Haskell-cafe] Matlab Style Logic Operations ala V1.*(V2>0) on Vectors and Matrices with HMatrix ??

Henning Thielemann lemming at henning-thielemann.de
Sun Dec 26 00:52:40 CET 2010

On Sat, 25 Dec 2010, gutti wrote:

> this line works :
> matrixfunction x y = liftMatrix2 (zipVectorWith(\a1 a2 -> if a2>=0 then a1 else 0)) x y
> but when I use this line :
> matrixfunction f x y = liftMatrix2 (zipVectorWith f) x y
> how can / do I have to define f in a seperate line a way, that it works and
> gives the same result ?

The same way you have literally replaced
   (\a1 a2 -> if a2>=0 then a1 else 0)
  by 'f' at the right hand side, you can use that phrase as argument to the 
parameter 'f':

   matrixfunction (\a1 a2 -> if a2>=0 then a1 else 0) x y

The lambda expression (\ ...) really is just a notation for a function.

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