Dear Haskellers,
 
since this is my first post,
 
    "Hello all"
 
I have a problem with a function taken from class Arrow.
 
    arr :: (b -> c) -> a b c
 
To build my own arrow, i need to distinguish between different kinds of b or c.
For instance, if b has the form (d,e), i want to construct something different as when having form (d,e,f).
 
Could I get a hint how to express my needs, please!
 
Many thanks in advance
 
 
Sven Biedermann