Re: [Haskell-beginners] Trying to write netwire combiner similar to multicast

On 11/06/2012 02:44 AM, Ertugrul Söylemez wrote:

Nathan Hüsken wrote:

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Also your interface seems very unsafe to me. I suggest the following interface instead:

shrinking :: (Monad m) => [Wire e m a b] -> Wire e m a [b]

Then normally 'a' could be something like Map K A.

That would mean, the individual wires have to know there own id?!? Mmmh, I will try to keep this bookkeeping out of the wires with this interface:

shrinking :: (Monad m) => [Wire e m a b] -> Wire e m (Map Int a) (Int,b)

shrinking will assign the ids to the wires and returns them with the result. I will see where this gets me ... :).

The problem with such an interface is the inflexibility. Notice that removing a subwire will change the numbering of all subsequent wires. The interface I suggested follows this basic idea:

shrinking :: (Monad m) => [(a' -> a, Wire e m a b)] -> Wire e m a' b

That should be ".. -> Wire e m a' [b]", correct?

The reasoning is that this way you disconnect the individual values from the positions in the subwire list. This will also make writing the combinator a bit simpler. If you will here is an interesting alternative:

data Subwire e m a b = forall a'. Subwire (a -> a') (Wire e m a' b)

shrinking :: (Monad m) => [Subwire e m a b] -> Wire e m a b

Ohh, the scary forall keyword :). Here it does nothing but hide the a' type from the type signature, is that correct? Thanks! Nathan