Greatest Common Divisor and Least Common Multiple functions in Haskell

Recently, I wrote a post about finding the gcd and lcm with C: http://knowledge-aholic.blogspot.com/2009/11/greatest-common-divisor-and-least.html

Since then, I have started Haskell and here is how implemented the "same" functions with Haskell (note that with Haskell, I have to use recursion to find the gcd) :

mygcd :: Int -> Int -> Int
mygcd n m
 | m == 0 = n
 | otherwise = mygcd m (mod n m)
 
mylcm :: Int -> Int -> Int
mylcm n m = div (n * m) (mygcd n m) 

An elegant Fibonacci solution with Haskell

Here's a very elegant Fibonacci solution I found in Simon Thompson's book, The Craft of Functional Programming:

--Given a tuple with a fibonacci pair, this function returns another tuple with
--the next two numbers in the sequence
fibStep :: (Int, Int) -> (Int, Int)
fibStep (u,v) = (v, u + v)

--The Definition for the Fibonacci pair
fibPair :: Int -> (Int, Int)
fibPair n
| n == 0 = (0,1)
| otherwise = fibStep (fibPair (n - 1))

--Pass the output of the fibPair function to Haskell's fst function,
--which returns the first item in the given tuple
fastFib :: Int -> Int
fastFib = fst . fibPair