import Data.Ratio

myEnumFromThen     :: (Fractional a) => a -> a -> [a]
myEnumFromThen n m = n `seq` m `seq` (n : myEnumFromThen m (m+m-n))

myEnumFromThenTo   :: (Ord a, Fractional a) => a -> a -> a -> [a]
myEnumFromThenTo e1 e2 e3
    = takeWhile predicate (myEnumFromThen e1 e2)
                                where
                                 predicate | e2 >= e1  = (<= e3)
                                           | otherwise = (>= e3)

main = do
    print $ (myEnumFromThenTo  1.5 1.8 2.999999999999999  :: [Float])
    print $ (myEnumFromThenTo 1.5 1.8 2.99999999999 :: [Ratio Int])
    print $ (myEnumFromThenTo 1.5 1.8 2.999999999   :: [Ratio Int])
    print $ (myEnumFromThenTo 1.5 1.8 2.9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999  :: [Ratio Integer])
    print $ (myEnumFromThenTo 0 (1%3) 2.9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999  :: [Ratio Integer])
    print $ (myEnumFromThenTo 0 (1%3) 3.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000  :: [Ratio Integer])
    print $ (myEnumFromThenTo 0 (1%3) 3.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001  :: [Ratio Integer])