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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
module Interpreter.Rep where
import Data.IORef
import qualified Data.Vector.Mutable as MV
import GHC.TypeError
import Array
import AST
type family Rep t where
Rep TNil = ()
Rep (TPair a b) = (Rep a, Rep b)
Rep (TEither a b) = Either (Rep a) (Rep b)
Rep (TMaybe t) = Maybe (Rep t)
Rep (TArr n t) = Array n (Rep t)
Rep (TScal sty) = ScalRep sty
Rep (TAccum t) = IORef (RepAc t)
type family RepAc t where
RepAc TNil = ()
RepAc (TPair a b) = (RepAc a, RepAc b)
-- This is annoying when working with values of type 'RepAc t', because
-- failing a pattern match does not generate negative type information.
-- However, it works, saves us from having to defining a LEither type
-- first-class in the type system with
-- Rep (LEither a b) = Maybe (Either a b)
-- and it's not even incorrect, in a way.
RepAc (TMaybe (TEither a b)) = IORef (Maybe (Either (RepAc a) (RepAc b)))
RepAc (TMaybe t) = IORef (Maybe (RepAc t))
RepAc (TArr n t) = (Shape n, MV.IOVector (RepAc t))
RepAc (TScal sty) = IORef (ScalRep sty)
RepAc (TAccum t) = TypeError (Text "Nested accumulators")
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