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.Common
  16 import Language.Symantic.Expr.Eq
  17
  18 -- * Class 'Sym_Ord'
  19 -- | Symantic.
  20 class Sym_Eq repr => Sym_Ord repr where
  21         compare :: Ord a => repr a -> repr a -> repr Ordering
  22         default compare :: (Trans t repr, Ord a)
  23                         => t repr a -> t repr a -> t repr Ordering
  24         compare = trans_map2 compare
  25
  26 -- * Type 'Expr_Ord'
  27 -- | Expression.
  28 data Expr_Ord (root:: *)
  29 type instance Root_of_Expr      (Expr_Ord root)      = root
  30 type instance Type_of_Expr      (Expr_Ord root)      = Type_Ordering
  31 type instance Sym_of_Expr       (Expr_Ord root) repr = (Sym_Ord repr)
  32 type instance Error_of_Expr ast (Expr_Ord root)      = No_Error_Expr
  33
  34 compare_from
  35  :: forall root ty ast hs ret.
  36  ( ty ~ Type_Root_of_Expr (Expr_Ord root)
  37  , Lift_Type_Root Type_Ordering (Type_Root_of_Expr root)
  38  , Eq_Type (Type_Root_of_Expr root)
  39  , Expr_from ast root
  40  , Lift_Error_Expr (Error_Expr (Error_of_Type ast ty) ty ast)
  41                    (Error_of_Expr ast root)
  42  , Root_of_Expr root ~ root
  43  , Constraint_Type Ord ty
  44  ) => ast -> ast
  45  -> Expr_From ast (Expr_Ord root) hs ret
  46 compare_from ast_x ast_y ex ast ctx k =
  47         expr_from (Proxy::Proxy root) ast_x ctx $
  48          \(ty_x::Type_Root_of_Expr root h_x) (Forall_Repr_with_Context x) ->
  49         expr_from (Proxy::Proxy root) ast_y ctx $
  50          \(ty_y::Type_Root_of_Expr root h_y) (Forall_Repr_with_Context y) ->
  51         check_eq_type ex ast ty_x ty_y $ \Refl ->
  52         check_constraint_type ex (Proxy::Proxy Ord) ast ty_x $ \Dict ->
  53         k type_ordering $ Forall_Repr_with_Context $
  54          \c -> x c `compare` y c