Language/Symantic/Expr/Ord.hs

   1 {-# LANGUAGE DefaultSignatures #-}
   2 {-# LANGUAGE FlexibleContexts #-}
   3 {-# LANGUAGE ScopedTypeVariables #-}
   4 {-# LANGUAGE TypeFamilies #-}
   5 {-# LANGUAGE TypeOperators #-}
   6 -- | Expression for 'Ord'.
   7 module Language.Symantic.Expr.Ord where
   8
   9 import Data.Proxy (Proxy(..))
  10 import Data.Type.Equality ((:~:)(Refl))
  11 import Prelude hiding (compare)
  12
  13 import Language.Symantic.Trans.Common
  14 import Language.Symantic.Type
  15 import Language.Symantic.Expr.Root
  16 import Language.Symantic.Expr.Error
  17 import Language.Symantic.Expr.From
  18 import Language.Symantic.Expr.Eq
  19
  20 -- * Class 'Sym_Ord'
  21 -- | Symantic.
  22 class Sym_Eq repr => Sym_Ord repr where
  23         compare :: Ord a => repr a -> repr a -> repr Ordering
  24         default compare :: (Trans t repr, Ord a)
  25                         => t repr a -> t repr a -> t repr Ordering
  26         compare = trans_map2 compare
  27
  28 -- * Type 'Expr_Ord'
  29 -- | Expression.
  30 data Expr_Ord (root:: *)
  31 type instance Root_of_Expr      (Expr_Ord root)      = root
  32 type instance Type_of_Expr      (Expr_Ord root)      = Type_Ordering
  33 type instance Sym_of_Expr       (Expr_Ord root) repr = (Sym_Ord repr)
  34 type instance Error_of_Expr ast (Expr_Ord root)      = No_Error_Expr
  35
  36 compare_from
  37  :: forall root ty ast hs ret.
  38  ( ty ~ Type_Root_of_Expr (Expr_Ord root)
  39  , Lift_Type_Root Type_Ordering (Type_Root_of_Expr root)
  40  , Eq_Type (Type_Root_of_Expr root)
  41  , Expr_from ast root
  42  , Lift_Error_Expr (Error_Expr (Error_of_Type ast ty) ty ast)
  43                    (Error_of_Expr ast root)
  44  , Root_of_Expr root ~ root
  45  , Constraint_Type Ord ty
  46  ) => ast -> ast
  47  -> Expr_From ast (Expr_Ord root) hs ret
  48 compare_from ast_x ast_y ex ast ctx k =
  49         expr_from (Proxy::Proxy root) ast_x ctx $
  50          \(ty_x::Type_Root_of_Expr root h_x) (Forall_Repr_with_Context x) ->
  51         expr_from (Proxy::Proxy root) ast_y ctx $
  52          \(ty_y::Type_Root_of_Expr root h_y) (Forall_Repr_with_Context y) ->
  53         check_eq_type ex ast ty_x ty_y $ \Refl ->
  54         check_constraint_type ex (Proxy::Proxy Ord) ast ty_x $ \Dict ->
  55         k type_ordering $ Forall_Repr_with_Context $
  56          \c -> x c `compare` y c