Language/LOL/Symantic/Type/Var.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE GADTs #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# LANGUAGE Rank2Types #-}
   5 {-# LANGUAGE ScopedTypeVariables #-}
   6 {-# LANGUAGE TypeFamilies #-}
   7 {-# LANGUAGE TypeOperators #-}
   8 {-# LANGUAGE UndecidableInstances #-}
   9 -- | Type variable.
  10 module Language.LOL.Symantic.Type.Var
  11  ( module Language.LOL.Symantic.Type.Var
  12  , module Language.LOL.Symantic.Lib.Data.Peano
  13  ) where
  14
  15 import Data.Maybe (isJust)
  16
  17 import Language.LOL.Symantic.AST
  18 import Language.LOL.Symantic.Type.Common
  19 import Language.LOL.Symantic.Lib.Data.Peano
  20
  21 -- * Type 'Type_Var'
  22 -- | The variable type.
  23 data Type_Var (root:: * -> *) p where
  24         Type_Var :: SPeano p -> Type_Var root p
  25 type instance Root_of_Type      (Type_Var root) = root
  26 type instance Error_of_Type ast (Type_Var root) = ()
  27
  28 instance -- Type_Eq
  29  Type_Eq (Type_Var root) where
  30         type_eq (Type_Var x) (Type_Var y) = x `peano_eq` y
  31 instance -- Eq
  32  Eq (Type_Var root h) where
  33         x == y = isJust $ x `type_eq` y
  34 instance -- String_from_Type
  35  String_from_Type (Type_Var root) where
  36         string_from_type (Type_Var p) =
  37                 "a" ++ show (integral_from_peano p::Integer)
  38 instance -- Show
  39  Show (Type_Var root h) where
  40         show = string_from_type
  41 instance -- Type_from AST
  42  ( Error_Type_Lift (Error_Type AST) (Error_of_Type AST root)
  43  , Implicit_HBool (Is_Last_Type (Type_Var root) root)
  44  ) => Type_from AST (Type_Var root) where
  45         type_from px_ty ast _k =
  46                 Left $ error_type_unsupported px_ty ast
  47
  48 -- | Convenient alias to include a 'Type_Var' within a type.
  49 type_var :: Type_Root_Lift Type_Var root => SPeano p -> root p
  50 type_var = type_root_lift . Type_Var