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polysemy-research / polysemy-zoo

:monkey::panda_face: Experimental, user-contributed effects and interpreters for polysemy
BSD 3-Clause "New" or "Revised" License
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Add fixedNat and friend to IdempotentLowering #10

Closed isovector closed 5 years ago

isovector commented 5 years ago

The following functions should exist in Polysemy.IdempotentLowering:


fixedNat
    :: forall m n base
     . Applicative base
    => ((forall x. m x -> n x) -> (forall x. m x -> n x))
    -> base (forall x. m x -> n x)
fixedNat f =
  let x :: (forall x. m x -> n x)
      x = f x
   in nat x

fixedNat'
    :: forall m n f base
     . Applicative base
    => ((forall x. m x -> n (f x)) -> (forall x. m x -> n (f x)))
    -> base (forall x. m x -> n (f x))
fixedNat' f =
  let x :: (forall x. m x -> n (f x))
      x = f x
   in nat' x

What's going on with these? They are like nat but for higher-order interpreters that need access to themselves! Usage:

fixedNat $ \me -> interpretH $ \case