On Mon, Jan 28, 2013 at 5:43 PM, Bob Hutchison <hutch-li...@recursive.ca>wrote:
> > Now, this is how I got caught: it seems to be impossible to have > collections of things with a common type class if they have different > types. How is it that I've written that many lines of code in Haskell and > I'm just noticing this now? (If I wasn't so annoyed, I'd look for something > clever to reflect how loc count obviously doesn't mean much… but clever > seems to be beyond me today). > > Is this true? Are there any GHC extensions that will let me around this? > I just encountered this recently myself. There is a GADT extension [1][2] that may help. The greater abstraction appears to lie in existential types [3]. That being said, I'm a beginner as well and haven't yet used these extensions. So far I have found that my code is simplified by redefining heterogeneous types in terms of homogeneous functions. If I have a class that implements common methods, I will reorganize lists by common function types rather than by class. Cheers, Darren --- [1] http://www.haskell.org/haskellwiki/GADT [2] http://www.haskell.org/haskellwiki/GADTs_for_dummies [3] http://www.haskell.org/haskellwiki/Existential_type
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