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

[David Banas]

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 <will.yager at gmail.com> 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 <capn.freako at gmail.com> 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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