Language/Symantic/Type/Var.hs

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