On 14 jun 2010, at 07:42, Aran Donohue wrote:
Hi Cafe,
I've been doing Haskell for a few months, and I've written some mid-sized programs and many small ones. I've read lots of documentation and many papers, but I'm having difficulty making the jump into some of the advanced concepts I've read about.
How do people build intuitions for things like RankNTypes and arrows? (Is the answer "Get a PhD in type theory?") Normally I learn by coding up little exercise programs, but for these I don't have good intuitions about the kinds of toy problems I ought to try to solve that would lead me to understand these tools better.
I learned my advanced stuff in two ways: 1. I followed excellent courses at Utrecht University, where they teach (among other things) advanced functional programming. 2. I just read a lot, which is a lot slower than 1. 3. By building my own programs, I inevitably find my self stuck and while searching for a solution, sometimes these concepts are the answer. For example, once I had a monadic program and I wanted to serialize/inspect the program, which turned out to be impossible in my case. The solution was to write it down using arrows (thus I had to learn arrows and also arrow-notatation). I think (for me) this is the most powerful way to learn new advanced concepts. I need practical problems to keep myself motivated.
For systems like Template Haskell and SYB, I have difficulty judging when I should use Haskell's simpler built-in semantic abstractions like functions and typeclasses and when I should look to these other mechanisms.
Sometimes Template Haskell or SYB is the answer, and it's a matter of style, but I try to avoid them as much as possible. I find that generic programming in the style of regular [1] or emgm [2] is often much simpler. Some more tips: subscribe to planet haskell, if you haven't done that already. Try to find ICFP/JFP/etc papers online that interest you. -chris [1]: http://hackage.haskell.org/package/regular [2]: http://hackage.haskell.org/package/emgm