2007/8/15, Alexteslin <[EMAIL PROTECTED]>: > I am really sorry, but i still can't define the function. The chapter the > exercise is in precedes algebraic types or Maybe a types. And is seems that > must being easy to define.
If you don't have Maybe, you still have it's older brother, namely lists (as strongly hinted by Jon Fairbairn). > so you need an f so that c `f` x is c (for any c and x) and > yet (b `f` c) is c for any c and b -- this is impossible (or > I'm asleep). Well, it isn't "impossible" but quite hard (and not even standard H98 if I'm not mistaken) and obviously not in the range of the possibilities here. Still you could "approximate" it, and in fact I believe the [Char] -> Char requirement is hinting at such a (arguably and IMO ugly) solution. For example you could assume there would be no "NUL" character in a string ([Char] is a synonym for String, or vice-versa), and then get a simple myLast for String in this restrictive case (and looking exactly like Alexteslin sample). -- Jedaï _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
