How can I implement this arrow? Thanks

[Ross Paterson]

On Tue, Sep 16, 2003 at 02:32:48PM -0500, Yu Di wrote:
> What I am trying to do is to use Haskell to simulate some process, and 
> meanwhile collecting information about the data-flow throughout the whole 
> process into the output. The (String, a) example is just a simplified 
> version of that. Thanks for pointing out my mistakes, I will try to do it 
> as a decorated-data combinator.

This sounds a bit like the example in

	http://www.soi.city.ac.uk/~ross/talks/fop.4.ps.gz

The idea is to define your network as a generic arrow, and instantiate
it differently for different interpretations.  For simulation, one
can use Stream i -> Stream o, though there are other possibilities.
To get a map, you use a state transformer (with the map as the state),
and pass edge labels through the arrows.

I think the reason you're getting in a tangle is that you're trying to
do both with the same interpretation.