http://blog.tmorris.net The weblog of Tony Morris Thu, 17 Jul 2008 20:15:37 +0000 http://backend.userland.com/rss092 en The exercises below are similar to my previous 'Scala exercises for beginners', except the rules a little clearer. For those of who have emailed me or submitted responses here on the blog, I will get around to providing you feedback, however, I'd prefer to do so on the revised version ... http://blog.tmorris.net/haskell-exercises-for-beginners/ The following exercises have come from of a course that I give on Functional Programming. I have assigned them difficulty ratings to make it a bit more exciting. Download the compilable source code from here or find it below. Enjoy :) These exercises can be translated into any language powerful enough ... http://blog.tmorris.net/scala-exercises-for-beginners/ When some programmers pick up a functional programming language like Microsoft Excel, they stop caring about identifier names. A1 = blah B1 = function(A1, C2) ... Can this observation be explained while maintaining consistency? I think it can. http://blog.tmorris.net/just-an-observation/ Some programmers are married to the imperative, side-effecting mindset. This makes them fearful of Scala's implicit keyword (among many other high-level programming constructs and abstractions). You can read all sorts of amateurish criticism of this language construct on various websites, but I plan to show why they are a necessity ... http://blog.tmorris.net/implicits-for-the-fearless/ Here is the Applicative functor type-class (see Applicative Programming with Effects, Conor McBride, Ross Paterson): class Applicative f where pure :: a -> f a () :: f (a -> b) -> f a -> f b Here are the laws for the Applicative functor type-class: identity pure id ... http://blog.tmorris.net/applicative-functor-laws-using-reductio-scala/ Runar recently made mention of these so-called Functors and Monads in his excellent post about concurrency/actors in Java. There are all sorts of tutorials out there for understanding what a Monad is, however, I am of the opinion that one must first understand what a Functor is. This is because ... http://blog.tmorris.net/just-what-the-funk-is-a-functor-anyway/ In the spirit of yesterday's post that denoted the Functor Laws using Reductio, I will also give the Monad Laws. Before I do however, here is an example use of the FunctorLaws object that runs 600 unit tests when testing a Functor implementation for scala.Option[A], scala.List and finally, for the ... http://blog.tmorris.net/monad-laws-using-reductio-scala/ A somewhat intricate and extremely useful code snippet using Reductio for testing the laws of any Functor instance (note that the Functor type is part of Scalaz): import reductios.Property._ import reductios.Arbitrary import reductio.Coarbitrary import reductios.Arbitrary._ object FunctorLaws { def identity[F[_], A](implicit f: Functor[F], af: Arbitrary[F[A]]) = prop((fa: F[A]) => f.fmap((a: ... http://blog.tmorris.net/functor-laws-using-reductio-scala/ Many people struggle to understand those fluffy things called Monads and why they are important. I'm not going to attempt to alleviate this to a large degree, but I have had a recent success with a friend in having them attempt to write a familiar Scala function as a method. ... http://blog.tmorris.net/youd-naturally-write-flatmap-yourself-if-asked-the-question/ From http://www.news.com.au/comments/0,23600,23907216-462,00.html on the recent price rise by ABC Learning Centres (i.e. child care): ABC Learing centres have now increased there fees three times since early 2007. There justification for these raises in no way benefit the children in they're care or they're staff!. http://blog.tmorris.net/abc-learning-centres-required-for-adults/