Can someone provide a hand calculation of:

    span (< 0) [-1, -2, -3, 0, 1, 2, -3, -4, -5]?

I know the result is ([-1, -2, -3], [0, 1, 2, -3, -4, -5]), but the recursion flummoxes me.

Here's the Prelude definition:

    mySpan                     :: (a -> Bool) -> [a] -> ([a], [a])

    mySpan _ []                =  ([], [])

    mySpan p xs@(x:xs')

        | p x                  =  (x:ys, zs)

        | otherwise            =  ([], xs)

                               where

                                   (ys, zs) = mySpan p xs'

Thanks.

---

Hotmail has tools for the New Busy. Search, chat and e-mail from your inbox. Learn more.