Sorry to take offense :-) maybe I was being too modest? What leads me to conclude that is... Reading several papers about uses of Arrows and Applicative and Monads for parsing and FRP, being on the mailing-lists for a few years listening to debates and people struggling with bits of code, getting a sense of the history of each abstraction and of how people who use that abstraction daily relate to it. (let's see if I can name names... Ross Paterson, Conor McBride, maybe Simon Peyton-Jones..). Experimenting a bit with my own code. Having a vague sense, through coding Haskell quite a bit, how much it's possible to condense a piece of code. It is not a conclusion of compulsion, just that I haven't seen it done better. It seems Arrows are a necessary abstraction for a couple very particular world-views/paradigms, and don't fit very well with a lot of other stuff. So far, I haven't used FRP for anything major, and I've done most parsing with Parsec (monad-based) and Happy (hmm, it's a preprocessor). Since I don't have lots of experience with the examples, I didn't want to claim to understand the abstraction(class) very well. :-) -Isaac Tony Morris wrote:
If you don't yet understand Arrows, then what compels you to conclude that there are more idiomatic solutions (than what you don't yet understand)? Just sayin'
Isaac Dupree wrote:
Philip Scott wrote:
Thanks John,
Every module can have its own definition for each name, such as the operator (+). So in your module (eg. module Main, or module DateValueSeries), you can go ahead and define your own (+). The major caveat is making sure you don't conflict with the default (+), which lives in module Prelude, which is normally automatically brought into scope. That actually quite nicely solves the problem... it feels almost a little too easy, after spending the evening getting my mind wrapped up with Arrows :) why has no one mentioned: you most likely don't need to understand Arrows? I'm pretty good with Haskell, and Arrows are still somewhat confusing to me. Why? Most problems I've worked with in Haskell have had more-idiomatic solutions than Arrows. (examples include: Monad; Functor; Applicative; just plain functions; plain old lack of type-class abstraction.) It's not so easy or useful to understand any abstraction/class without using at least two or three useful examples/instances of it first.
-Isaac _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners