Amount.hs:

module Money
(
    Currency
) where

class (Eq a, Show a) => Currency a where
    code :: a -> String
    intSep :: a -> Char
    decSep :: a -> Char
    symbol :: a -> String
    decPlaces :: a -> Word8


Currencies.hs:

import qualified Money(Amount, Currency)

data COP = COP
instance Money.Currency COP where
    code = "COP"
    intSep = '.'
    decSep = ','
    symbol = "$"
    decPlaces = 2