let x = very_long_computation
in x + x

##</code><code>##

import System.Time( getClockTime )

add_up 0 acc = acc
add_up n acc = add_up (n - 1) (acc + n)

time = getClockTime >>= print

main = do
    time
    print (add_up 10000000 0)
    time
    print (add_up 5000000 0)
    time
    putStrLn "enter number to add up to..."
    val <- getLine 
    time
    print (add_up (read val) 0)
    time