Language/Symantic/Type/Var.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE GADTs #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# LANGUAGE TypeFamilies #-}
   5 {-# OPTIONS_GHC -fno-warn-missing-methods #-}
   6 -- | Type variable.
   7 module Language.Symantic.Type.Var
   8  ( module Language.Symantic.Type.Var
   9  , module Language.Symantic.Lib.Data.Peano
  10  ) where
  11
  12 import Data.Maybe (isJust)
  13
  14 import Language.Symantic.Type.Common
  15 import Language.Symantic.Lib.Data.Peano
  16
  17 -- * Type 'Type_Var'
  18 -- | The variable type.
  19 data Type_Var (root:: * -> *) p where
  20         Type_Var :: SPeano p -> Type_Var root p
  21 type instance Root_of_Type      (Type_Var root) = root
  22 type instance Error_of_Type ast (Type_Var root) = No_Error_Type
  23
  24 instance -- Eq_Type
  25  Eq_Type (Type_Var root) where
  26         eq_type (Type_Var x) (Type_Var y) = x `peano_eq` y
  27 instance -- Eq
  28  Eq (Type_Var root h) where
  29         x == y = isJust $ x `eq_type` y
  30 instance -- String_from_Type
  31  String_from_Type (Type_Var root) where
  32         string_from_type (Type_Var p) =
  33                 "t" ++ show (integral_from_peano p::Integer)
  34 instance -- Show
  35  Show (Type_Var root h) where
  36         show = string_from_type
  37 instance Constraint_Type Eq  (Type_Var root)
  38 instance Constraint_Type Ord (Type_Var root)
  39 instance Unlift_Type1 Type_Var
  40 instance Eq_Type1 (Type_Var root)
  41
  42 -- | Convenient alias to include a 'Type_Var' within a type.
  43 type_var :: Lift_Type_Root Type_Var root => SPeano p -> root p
  44 type_var = lift_type_root . Type_Var