Language/Symantic/Type/Maybe.hs

   1 {-# LANGUAGE FlexibleContexts #-}
   2 {-# LANGUAGE FlexibleInstances #-}
   3 {-# LANGUAGE MultiParamTypeClasses #-}
   4 {-# LANGUAGE PatternSynonyms #-}
   5 {-# LANGUAGE TypeFamilies #-}
   6 {-# OPTIONS_GHC -fno-warn-orphans #-}
   7 module Language.Symantic.Type.Maybe where
   8
   9 import Data.Proxy
  10 import Data.Type.Equality ((:~:)(Refl))
  11 import Language.Symantic.Type.Root
  12 import Language.Symantic.Type.Type0
  13 import Language.Symantic.Type.Type1
  14
  15 -- * Type 'Type_Maybe'
  16 -- | The 'Maybe' type.
  17 type Type_Maybe = Type_Type1 (Proxy Maybe)
  18
  19 pattern Type_Maybe :: root a -> Type_Maybe root (Maybe a)
  20 pattern Type_Maybe a = Type_Type1 Proxy a
  21
  22 instance Constraint_Type Eq root => Constraint_Type Eq (Type_Maybe root) where
  23         constraint_type c (Type_Type1 _ a)
  24          | Just Dict <- constraint_type c a
  25          = Just Dict
  26         constraint_type _c _ = Nothing
  27 instance Constraint_Type Ord root => Constraint_Type Ord (Type_Maybe root) where
  28         constraint_type c (Type_Type1 _ a)
  29          | Just Dict <- constraint_type c a
  30          = Just Dict
  31         constraint_type _c _ = Nothing
  32 instance Constraint_Type Monoid root => Constraint_Type Monoid (Type_Maybe root) where
  33         constraint_type c (Type_Type1 _ a)
  34          | Just Dict <- constraint_type c a
  35          = Just Dict
  36         constraint_type _c _ = Nothing
  37 instance Constraint_Type1 Functor (Type_Maybe root) where
  38         constraint_type1 _c (Type_Type1 _ _) = Just Dict
  39 instance Constraint_Type1 Applicative (Type_Maybe root) where
  40         constraint_type1 _c (Type_Type1 _ _) = Just Dict
  41 instance Constraint_Type1 Foldable (Type_Maybe root) where
  42         constraint_type1 _c (Type_Type1 _ _) = Just Dict
  43 instance Constraint_Type1 Traversable (Type_Maybe root) where
  44         constraint_type1 _c (Type_Type1 _ _) = Just Dict
  45 instance Constraint_Type1 Monad (Type_Maybe root) where
  46         constraint_type1 _c Type_Type1{} = Just Dict
  47 instance -- Eq_Type
  48  Eq_Type root =>
  49  Eq_Type (Type_Maybe root) where
  50         eq_type (Type_Type1 _px1 a1) (Type_Type1 _px2 a2)
  51          | Just Refl <- a1 `eq_type` a2
  52          = Just Refl
  53         eq_type _ _ = Nothing
  54 instance -- Eq_Type1
  55  Eq_Type1 (Type_Maybe root) where
  56         eq_type1 Type_Type1{} Type_Type1{}
  57          = Just Refl
  58 instance -- String_from_Type
  59  String_from_Type root =>
  60  String_from_Type (Type_Maybe root) where
  61         string_from_type (Type_Type1 _f a) =
  62                 "Maybe" ++ " (" ++ string_from_type a ++ ")"
  63
  64 -- | Inject 'Type_Maybe' within a root type.
  65 type_maybe
  66  :: Lift_Type_Root Type_Maybe root
  67  => root h_a
  68  -> root (Maybe h_a)
  69 type_maybe = lift_type_root . Type_Type1 (Proxy::Proxy Maybe)