arrows

So I'll break my question into 4 parts, but first some background: I feel relatively comfortable with Monads, but not very comfortable with Arrows. I suppose the main problem I have with them is, I don't see what they are useful for. Whether formally correct or not, I understand Monads to be a tool that allows us to introduce side effects from computation. As they generalize program fragments from pure values to values boxed with other actions. From my shotgun "read all the papers" approach to learning about arrows, I've come across two conflicting viewpoints: A. Arrows are more powerful than

I'm using the Fancybox integration with Pikachoose as explained here: http://www.pikachoose.com/how-to-fancybox/ I'm trying to get the lightbox to display next and previous arrows but not on the pikachoose stage and I'm having a bit of trouble. I tried to add the options of showNavArrows: true in the fancybox section of the script but it wouldn't work. So then I tried the nav options on pikachoose to display using this: {text: {previous: "Previous", next: "Next" }} but I keep getting an error, possibly my syntax isn't going in the right place? Can someone help please? this is the code I'm

When I try to pattern-match a GADT in an proc syntax (with Netwire and Vinyl): sceneRoot = proc inputs -> do let (Identity camera :& Identity children) = inputs returnA -< (<*>) (map (rGet draw) children) . pure I get the (rather odd) compiler error, from ghc-7.6.3 My brain just exploded I can't handle pattern bindings for existential or GADT data constructors. Instead, use a case-expression, or do-notation, to unpack the constructor. In the pattern: Identity cam :& Identity childs I get a similar error when I put the pattern in the proc (...) pattern. Why is this? Is it unsound, or just