{-# LANGUAGE TypeFamilies #-}

-- | The core Futhark AST is parameterised by a @rep@ type parameter,
-- which is then used to invoke the type families defined here.
module Futhark.IR.Rep
  ( RepTypes (..),
    Op,
    NoOp (..),
    module Futhark.IR.RetType,
  )
where

import Data.Kind qualified
import Futhark.IR.Prop.Types
import Futhark.IR.RetType
import Futhark.IR.Syntax.Core (DeclExtType, DeclType, ExtType, Type)

-- | Returns nothing and does nothing.  Placeholder for when we don't
-- really want an operation.
data NoOp rep = NoOp
  deriving (Eq, Ord, Show)

-- | A collection of type families giving various common types for a
-- representation, along with constraints specifying that the types
-- they map to should satisfy some minimal requirements.
class
  ( Show (LetDec l),
    Show (ExpDec l),
    Show (BodyDec l),
    Show (FParamInfo l),
    Show (LParamInfo l),
    Show (RetType l),
    Show (BranchType l),
    Show (Op l),
    Eq (LetDec l),
    Eq (ExpDec l),
    Eq (BodyDec l),
    Eq (FParamInfo l),
    Eq (LParamInfo l),
    Eq (RetType l),
    Eq (BranchType l),
    Eq (Op l),
    Ord (LetDec l),
    Ord (ExpDec l),
    Ord (BodyDec l),
    Ord (FParamInfo l),
    Ord (LParamInfo l),
    Ord (RetType l),
    Ord (BranchType l),
    Ord (Op l),
    IsRetType (RetType l),
    IsBodyType (BranchType l),
    Typed (FParamInfo l),
    Typed (LParamInfo l),
    Typed (LetDec l),
    DeclTyped (FParamInfo l)
  ) =>
  RepTypes l
  where
  -- | Decoration for every let-pattern element.
  type LetDec l :: Data.Kind.Type

  type LetDec l = Type

  -- | Decoration for every expression.
  type ExpDec l :: Data.Kind.Type

  type ExpDec l = ()

  -- | Decoration for every body.
  type BodyDec l :: Data.Kind.Type

  type BodyDec l = ()

  -- | Decoration for every (non-lambda) function parameter.
  type FParamInfo l :: Data.Kind.Type

  type FParamInfo l = DeclType

  -- | Decoration for every lambda function parameter.
  type LParamInfo l :: Data.Kind.Type

  type LParamInfo l = Type

  -- | The return type decoration of function calls.
  type RetType l :: Data.Kind.Type

  type RetType l = DeclExtType

  -- | The return type decoration of branches.
  type BranchType l :: Data.Kind.Type

  type BranchType l = ExtType

  -- | Type constructor for the extensible operation.  The somewhat
  -- funky definition is to ensure that we can change the "inner"
  -- representation in a generic way (e.g. add aliasing information)
  -- In most code, you will use the 'Op' alias instead.
  type OpC l :: Data.Kind.Type -> Data.Kind.Type

  type OpC l = NoOp

-- | Apply the 'OpC' constructor of a representation to that
-- representation.
type Op l = OpC l l