On Tuesday 25 October 2005 08:36 pm, [EMAIL PROTECTED] wrote: > Hi, > My name is Michael. I'm new to Haskell. I'm working through > The Craft of Functional Programming by Simon Thompson. > I'm having problems with a few exercises from chapter 4. I will > present one per post. > > This one is from 4.9 > Given a function f of type Int -> Int give a recursive definition > of a function of type Int -> Int which on input n returns the maximum > values f 0, f 1, ... , f n > > I defined f as follows > f 0 = 0 > f 1 = 44 > f 2 = 5 > f 9 = 8
Most likely your problem is that f is only defined for input values 0, 1, 2 and 9. If you call f with any other value, you will end up with an error. > this works except when f n > n. In that case I get an "illegal > instruction" error and hugs exits. > I'm pretty sure this is a logic problem. Could someone point me > in the right direction so I can think about this problem correctly. > Here is my code > > maxOverf :: Int -> Int > maxOverf m > > | f m > m = (f m) > | otherwise = (maxOverf m-1) Here you are calling f with successively decreasing values; that will run into areas where f is undefined for any value of m other than 1 or 2. > Any hints/help/flames welcome. Thanks Try a total rather than a partial function for f. You can just add a default clause to the end, like f _ = 0 which will define f x to be 0 for all values of x except the ones already mentioned. _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
