Language/LOL/Symantic/Type/Bool.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE GADTs #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# LANGUAGE OverloadedStrings #-}
   5 {-# LANGUAGE TypeFamilies #-}
   6 {-# LANGUAGE UndecidableInstances #-}
   7 module Language.LOL.Symantic.Type.Bool where
   8
   9 import Data.Maybe (isJust)
  10 import Data.Type.Equality ((:~:)(Refl))
  11
  12 import Language.LOL.Symantic.AST
  13 import Language.LOL.Symantic.Type.Common
  14 import Language.LOL.Symantic.Type.Fun
  15
  16 -- * Type 'Type_Bool'
  17
  18 -- | The 'Bool' type.
  19 data Type_Bool (root:: * -> *) h where
  20         Type_Bool :: Type_Bool root Bool
  21 type instance Root_of_Type (Type_Bool root) = root
  22 type instance Error_of_Type ast (Type_Bool root) = Error_Type_Fun ast
  23
  24 instance -- Type_Eq
  25  Type_Eq (Type_Bool root) where
  26         type_eq Type_Bool Type_Bool = Just Refl
  27 instance -- Eq
  28  Eq (Type_Bool root h) where
  29         x == y = isJust $ type_eq x y
  30 instance -- Type_from AST
  31  ( Type_Root_Lift Type_Bool root
  32  , Error_Type_Lift (Error_Type_Fun AST) (Error_of_Type AST root)
  33    -- NOTE: require UndecidableInstances.
  34  ) => Type_from AST (Type_Bool root) where
  35         type_from _px_ty ast k =
  36                 case ast of
  37                  AST "Bool" asts ->
  38                         case asts of
  39                          [] -> k $ type_root_lift Type_Bool
  40                          _ -> Left $ Just $ error_type_lift $
  41                                 Error_Type_Fun_Wrong_number_of_arguments 0 ast
  42                  _ -> Left Nothing
  43 instance -- String_from_Type
  44  String_from_Type (Type_Bool root) where
  45         string_from_type Type_Bool = "Bool"
  46 instance -- Show
  47  Show (Type_Bool root h) where
  48         show = string_from_type
  49
  50 -- | Convenient alias to include a 'Type_Bool' within a type.
  51 type_bool :: Type_Root_Lift Type_Bool root => root Bool
  52 type_bool = type_root_lift Type_Bool
  53
  54 -- * Type 'Type_Fun_Bool'
  55 -- | Convenient alias.
  56 type Type_Fun_Bool lam = Type_Root (Type_Cons (Type_Fun lam) Type_Bool)