[Haskell-cafe] Why does this blow the stack?
brad.larsen at gmail.com
Fri Dec 21 12:48:09 EST 2007
On Fri, 21 Dec 2007 12:13:04 -0500, Justin Bailey <jgbailey at gmail.com>
> Given this function:
> dropTest n = head . drop n $ [1..]
> I get a stack overflow when n is greater than ~ 550,000 . Is that
> inevitable behavior for large n? Is there a better way to do it?
I'm curious as well. My first thought was to try the (!!) operator.
Prelude> [1..] !! 550000
overflows the stack on my computer, as does dropTest 550000.
The code for (!!) is apparently as follows:
xs !! n | n < 0 = error "Prelude.!!: negative index"
 !! _ = error "Prelude.!!: index too large"
(x:_) !! 0 = x
(_:xs) !! n = xs !! (n-1)
Isn't this tail recursive? What is eating up the stack?
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