On 14/06/10 06:42, 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.
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.
I'd second Ivan's suggestion to "learn-by-need". For SYB and Template
Haskell, and probably for most other fancy abstractions, you can get on
happily without them in most cases. When you start to think "there must
be a better way!" while coding, that's when you should start looking for
advanced features.
For example, if you find yourself writing the Nth boilerplate function
that pattern-matches all cases in your ADT just to apply a function in
its sub-types, that's when you'll want some form of generic programming
like SYB. And by that point you'll understand one of the problems that
generic programming solves, which is halfway towards understanding the
techniques themselves.
Hope that helps,
Neil.
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