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{-# OPTIONS -fglasgow-exts #-}
import PrelGHC
class EEq a where
(===), (/==) :: a -> a -> Bool
-- x /= y = not (x == y)
-- x == y = not (x /= y)
-- x /= y = True
(/==) x y = mynot ((===) x y)
x === y = True
data EOrdering = ELT | EEQ | EGT
mynot True = False
mynot False = True
{-
class (EEq a) => EOrd a where
ecompare :: a -> a -> EOrdering
(<<), (<<=), (>>>=), (>>>):: a -> a -> Bool
emax, emin :: a -> a -> a
-- An instance of Ord should define either compare or <=
-- Using compare can be more efficient for complex types.
ecompare x y
| x === y = EEQ
| x <<= y = ELT -- NB: must be '<=' not '<' to validate the
-- above claim about the minimal things that can
-- be defined for an instance of Ord
| otherwise = EGT
x <<= y = case ecompare x y of { EGT -> False; _other -> True }
x << y = case ecompare x y of { ELT -> True; _other -> False }
x >>>= y = case ecompare x y of { ELT -> False; _other -> True }
x >>> y = case ecompare x y of { EGT -> True; _other -> False }
-- These two default methods use '>' rather than compare
-- because the latter is often more expensive
emax x y = if x >>> y then x else y
emin x y = if x >>> y then y else x
-}
data EInt = EI Int#
ezeroInt, eoneInt, etwoInt, emaxInt, eminInt :: EInt
ezeroInt = EI 0#
eoneInt = EI 1#
etwoInt = EI 2#
eminInt = EI (-2147483648#) -- GHC <= 2.09 had this at -2147483647
emaxInt = EI 2147483647#
eeqInt (EI x) (EI y) = x ==# y
eneInt (EI x) (EI y) = x /=# y
instance EEq EInt where
(===) x y = x `eeqInt` y
(/==) x y = x `eneInt` y
main = putStr (if (ezeroInt === eoneInt) then "no!\n" else "yes!\n")
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