Thank you very much for introducing tail recursion. It's my first time to hear this. :) However, I'm wondering whether every loop structure from C like language can be translated to this kind of tail recursion? Yours, Hank -----Original Message----- From: Chris Kuklewicz [mailto:haskell@list.mightyreason.com] Sent: Tuesday, June 27, 2006 5:34 PM To: Huazhi (Hank) Gong Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] A question about stack overflow Huazhi (Hank) Gong wrote:
Hi, all
I'm just a newbie for Haskell and functional programming world. The idea I currently read is quite different and interesting.
I have one general question about the recursively looping style. For example:
myMax [ ] = error "empty list"
myMax [x] = x
myMax [x:xs] = if x>= (myMax xs) then x else (myMax xs)
I just list out this kind of very simple program. However, if the list size if a big number such as 10000000, the Winhug will report that the stack is overflow.
Does it mean that the functional programming is lacking of scalability? I do know that we can manually change the stack size for it. But that's not a good solution according to my opinion.
Yours, Hank
The function is not "tail recursive" Think about unfolding the recursion: mymax [1,2,3,4] = if 1 >= (if 2 >= (if 3 >= (4) then 3 else (4)) then 2 else (<above>)) then 1 else (<above>) If 4 is a long list, then the chain of "if" statements gets larger than size of the stack that the runtime will allow. The definition you have looks like a "right fold" where compare the head to the function applies to the remaining list and what you need is a "left fold" where you process the list so far then operate on the next element. -- Chris