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

[Henning Thielemann]

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.