On Wednesday 09 January 2002 10:59 am, you wrote: > diff f x = (f (x + epsilon) - f (x - epsilon)) / (2 * epsilon) > where epsilon = 0.00001 > > every call to say "diff sin" will cost you about as much as every call to > "sin" s/every call to "sin"/two calls to "sin"/ of course Alec