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Kind level promotion of polymorphic data constructors #99

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buggymcbugfix opened this issue Feb 26, 2019 · 1 comment

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buggymcbugfix commented Feb 26, 2019

Next item on the wishlist

data Maybe a = None | Some a

data InOrOut : Bool -> Type -> Type where
  In : forall {a : Type} . a -> InOrOut (Some ()) a;
  Out : forall {a : Type} . InOrOut None a

test : forall {m : Maybe Int} . InOrOut b Int -> InOrOut b Int
test (In x) = In (x * 2);
test Out = Out

lala : forall {m : Maybe Int} . InOrOut (Some ()) Int -> Int
lala (In x) = x

https://github.com/granule-project/granule/blob/master/work-in-progress/promote-data-poly.gr

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GuiltyDolphin commented Apr 2, 2019

I think I have a partial implementation for this (from some random fiddling), so you could do, e.g.,

data Bool = True | False
data Neg a = Not a

interface IsTrue a (b : a) Bool

instance {IsTrue a b True} => IsTrue (Neg a) (Not b) False

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