Language/Symantic/Interpreting/Dup.hs

   1 {-# LANGUAGE UndecidableInstances #-}
   2 -- | Interpreter to duplicate the representation of an expression
   3 -- in order to evaluate it with different interpreters.
   4 --
   5 -- NOTE: this is a more verbose, less clear,
   6 -- and maybe less efficient alternative
   7 -- to maintaining the universal polymorphism of @repr@ at parsing time
   8 -- as done with 'Forall_Repr_with_Context';
   9 -- it is mainly here for the sake of curiosity.
  10 module Language.Symantic.Interpreting.Dup where
  11
  12 import Data.Proxy
  13
  14 -- | Interpreter's data.
  15 data DupI repr1 repr2 a
  16  =   DupI
  17  {   dupI_1 :: repr1 a
  18  ,   dupI_2 :: repr2 a
  19  }
  20
  21 dupI0
  22  :: (cl r, cl s)
  23  => Proxy cl
  24  -> (forall repr. cl repr => repr a)
  25  -> DupI r s a
  26 dupI0 _cl f = f `DupI` f
  27
  28 dupI1
  29  :: (cl r, cl s)
  30  => Proxy cl
  31  -> (forall repr. cl repr => repr a -> repr b)
  32  -> DupI r s a
  33  -> DupI r s b
  34 dupI1 _cl f (a1 `DupI` a2) =
  35         f a1 `DupI` f a2
  36
  37 dupI2
  38  :: (cl r, cl s)
  39  => Proxy cl
  40  -> (forall repr. cl repr => repr a -> repr b -> repr c)
  41  -> DupI r s a
  42  -> DupI r s b
  43  -> DupI r s c
  44 dupI2 _cl f (a1 `DupI` a2) (b1 `DupI` b2) =
  45         f a1 b1 `DupI` f a2 b2
  46
  47 dupI3
  48  :: (cl r, cl s)
  49  => Proxy cl
  50  -> (forall repr. cl repr => repr a -> repr b -> repr c -> repr d)
  51  -> DupI r s a
  52  -> DupI r s b
  53  -> DupI r s c
  54  -> DupI r s d
  55 dupI3 _cl f (a1 `DupI` a2) (b1 `DupI` b2) (c1 `DupI` c2) =
  56         f a1 b1 c1 `DupI` f a2 b2 c2