import Debug.Trace

plus a b = trace ("Compute " ++ show a ++ " " ++ show b) (a + b)

fibs = 0 : 1 : zipWith (plus) fibs (tail fibs)

main :: IO ()
main =  do
print(take 10 fibs)
print(take 10 fibs)

import Debug.Trace

plus a b = trace ("Compute " ++ show a ++ " " ++ show b) (a + b)

makeFibs a b = fibs
         where fibs = a : b : zipWith (plus) fibs (tail fibs)

main :: IO ()
main = do
     print(take 10 fibs)
     print(take 10 fibs2)
           where fibs = makeFibs 0 1
                 fibs2 =  makeFibs 0 1

fibs2 =  makeFibs 1 2