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-- !!! test of cyclic default methods
--
class Foo a where
op1 :: Fractional b => a -> b -> Bool
op2 :: Fractional b => a -> b -> Bool
op3 :: Fractional b => a -> b -> Bool
op4 :: Fractional b => a -> b -> Bool
op5 :: Fractional b => a -> b -> Bool
op6 :: Fractional b => a -> b -> Bool
-- each depends on the next:
op1 a b = not (op2 a b)
op2 a b = not (op3 a b)
op3 a b = not (op4 a b)
op4 a b = not (op5 a b)
op5 a b = not (op6 a b)
op6 a b = not (op1 a b)
-- now some instance decls to break the cycle:
instance Foo Int where
op1 a b = a == 42
instance Foo Char where
op1 a b = a == 'c'
instance Foo a => Foo [a] where
op1 a b = null a
-- try it:
main = do
putStr (show (op2 (3::Int) 3.14159))
putStr (show (op2 'X' 3.14159))
putStr (show (op2 ([]::[Char])3.14159))
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