On Thu, 19 Jul 2007 10:55:19 -0700 (PDT), you wrote:
The question suggests to use some functions defined in the section, and one of them is iSort.
Aha. Well, that one certainly lends itself better to this particular proplen than either map or filter.
minimumValue :: [Int] -> Int minimumValue ns = head (iSort ns)
If I were going to use a sort, then yes, that's the way I would do it. Of course, sorting isn't the best way to solve the problem, as sorting will always be at least O(n * log n), whereas a more straightforward algorithm would be O(n).
The other question is to test whether the values of allEqual on inputs 0 to n are all equal. Again, I defined the method but not sure if its concise?
allEqual :: [Int] -> Bool allEqual xs = length xs == length (filter isEqual xs) where isEqual n = (head xs) == n
Simple recursion is probably the most conceptually straightforward approach here. One little difficulty with this problem (and with minimumValue, too) is that the problem isn't completely specified, because we don't know what answer we're supposed to give when the list is empty. Let's assume that allEqual is supposed to return True on an empty list. In that case, we can write it like this: allEqual :: [Int] -> Bool allEqual (x1:x2:xs) = ??? allEqual _ = ??? where the two ???s are left as an exercise for the reader. -Steve