Patrick Browne wrote:
Andrew, Thanks for your detailed feedback, it is a great help.
Well, I like to be helpful.
I appreciate that the code does not do anything useful, nor is it an appropriate way to write Haskell, but it does help me understand language constructs.
Personally, I find it easier to understand things when they do something meaningful, but sure.
I am studying the Haskell type class system as part of a language comparison. I am trying to exercise and understand the constructs rather than develop a meaningful application.
The best way to understand Haskell is... to completely forget everything you already know, and start again from scratch. ;-) Still, I gather that's not the point of this particular exercise. Since you're interested in comparisons... A method is simply a way of giving the same name to several different functions, and have the compiler pick the correct one based on the argument types. That's what methods do in OOP, and it's what they do in Haskell too. The notable difference is that in Haskell, all types are known at compile-time. (Unless you turn on certain extra non-standard language features...) The other point worth realising is that since Haskell has first-class functions, you don't "need" classes quite so much. (E.g., Java has the Runnable interface so that the JVM can call an object's run() method. In Haskell, you just say forkIO and pass it the function to execute. Similar deal for GUI callbacks and so forth.)