Collecting instantiated type class methods into an array.

Main.purs

module Main where

import Prelude
import Data.Array
import Debug
import Type.Prelude
import Type.Row
import Type.RowList
import Unsafe.Coerce
import Partial.Unsafe

class Refl a where
  refl :: a -> a
  
instance Refl Int where
  refl n = n + 1
  
instance Refl Number where
  refl n = n + 1.0
  
instance Refl String where
  refl n = n <> "no!"
  
class ReflRowList r where
  refls :: Proxy r -> Array (forall a. a -> a)
  
instance ReflRowList Nil where
  refls _ = []
  
else instance (ReflRowList r, Refl a) => ReflRowList (Cons n a r) where
  refls _ = unsafeCoerce [refl :: a -> a] <> refls (Proxy :: _ r)
  
type R = Cons "a" Int (Cons "b" Number (Cons "c" String Nil))

z = spy "help" (refls (Proxy :: _ R))

i = spy "int" $ (unsafePartial $ unsafeIndex z 0) 68

n = spy "number" $ (unsafePartial $ unsafeIndex z 1) 419.0

s = spy "string" $ (unsafePartial $ unsafeIndex z 2) "oh "