Try teaching Haskell using GADT-syntax
..using explicit kind signatures from the get 🐹
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GADT-syntax is the answer to :kind and :type
data Bool :: Type where
False :: Bool
True :: Bool
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Conversation
. o O ( Introduce legacy syntax.. as a shorthand once student understand kinds )
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Kind signatures are an essential tool for me to find patterns in Haskell
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Replying to
I think explicit kinds on stuff like the Functor type class would have greatly helped my comprehension initially:
class Functor (f :: Type -> Type) where
map :: forall a b. (a -> b) -> f a -> f b
Replying to
Learning `Maybe' as
data Maybe :: Type -> Type where ..
you as a student have been nudged towards make that connection (square in square hole) as you see Functor for the first time.
The output of :kind is always the form I prefer:
Functor :: (Type -> Type) -> Constraint
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Sadly type classes can't be written on that form :) oh well