On 28 December 2010 21:44, Edward Amsden
I'm writing a very similar library to Yampa. (I would be patching Yampa, but the code is a mess, so I decided to try starting from scratch.) Basically, I have a signal processing loop, where values are passed updated with a Maybe, representing whether there is or is not a change to the value. I could use a single Maybe around the whole thing, but that would require then re-updating a potentially large structure entirely. I want to be able to build a combinator that can combine two signal-fetching actions into a larger one:
Hi Edward That's a tough proposition - phrased in a different way, you want syntax (i.e algebraic data types) with holes. Functors (List, Data.Sequence, ...) and Bifunctors (pairs and Either, ...) have obvious holes, and working with holey things is possible[*] but its probably way too far out for signal processing where you have efficiency concerns. Is it common for Reactive libraries like Yampa to operate on a large "World" datatype - rather than streams of signals of some atomic unit like Double? If it were me, I'd want to answer this question first before attempting to represent it. [*] See Conor McBride's "Clowns and Jokers" for instance: http://personal.cis.strath.ac.uk/~conor/Dissect.pdf