Re: [Haskell-cafe] Question, re: type class syntax.

Hey David, I think there might be a bit of confusion here. When you say "LogTree2 a", that means "a" is an instance of "LogTree2". Maybe you want something like this? evaluator :: LogTree2 a => a -> SizedVector a -> SizedVector a Some context might help us to understand what you're going for. --Will On Sat, Aug 29, 2015 at 7:30 PM, David Banas wrote:

Thanks, Will. Maybe I’ve got the syntax all wrong, but my intent is just to constrain the type ’t’ to be of class 'LogTree2 a’. -db

On Aug 29, 2015, at 5:27 PM, William Yager wrote:

If you want the "LogTree2" typeclass to have multiple type arguments (which it looks like you do, from the definition of "evaluator"), you need to define it as

class (Show a, Num a) => LogTree2 a t where

--Will

On Sat, Aug 29, 2015 at 6:45 PM, David Banas wrote:

...

Hi all,

I can’t figure out why this is invalid:

class (Show a, Num a) => LogTree2 a where evaluator :: (LogTree2 a) t => t -> SizedVector a -> SizedVector a

error| ‘LogTree2’ is applied to too many type arguments In the type ‘(LogTree2 a) t => t -> SizedVector a -> SizedVector a’ In the class declaration for ‘LogTree2’

Can anyone help me understand?

Thanks, -db

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