Re: [Haskell-cafe] How to implement a digital filter, using Arrows?

On Wed, Oct 19, 2011 at 8:07 PM, Captain Freako wrote:

One more question on the `runAuto' code, John:

If I understand the code correctly, `f' is an arrow. Yet, we're using it on the right side of `=' in a simple assignment. How are we getting away with that?

Thanks, -db

liftAu' f s0 = proc x -> do

...

rec (y,s') <- arr f -< (x,s) s <- delay s0 -< s' returnA -< (y,s)

The value `f` is a function - a parameter of liftAu'. While all functions are arrows (Arrow is defined on (->)), the value `arr f` is an arrow of the automaton model. The `=` symbol is used to define the liftAu function. What are you imagining?