[Haskell-beginners] Ratio data constructor

[Galaxy Being]

I'm investigating rational numbers with Haskell. This is the source I've
found

data Ratio a = !a :% !a deriving (Eq)

reduce ::  (Integral a) => a -> a -> Ratio a
{-# SPECIALISE reduce :: Integer -> Integer -> Rational #-}
reduce _ 0              =  ratioZeroDenominatorError
reduce x y              =  (x `quot` d) :% (y `quot` d)
                           where d = gcd x y
(%) :: (Integral a) => a -> a -> Ratio a
x % y =  reduce (x * signum y) (abs y)

The Ratio data type would seem to be a parameterized type with two
parameters of the same type that must be "settled" in that they're not to
be lazily dealt with. Then the :% is the data constructor, the : meaning
it's a data constructor and not just an operation function. So this could
have been

data Ratio a = :% !a !a deriving (Eq)

correct? But then what confuses me is in reduce, why

reduce x y  =  (x `quot` d) :% (y `quot` d)

and not just %? We have :% defined in the data type and then (%) defined as
a function. What is going on here?

-- 
⨽
Lawrence Bottorff
Grand Marais, MN, USA
borgauf at gmail.com
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