[Haskell-cafe] Why does this blow the stack?

[Derek Elkins]

On Fri, 2007-12-21 at 09:56 -0800, David Benbennick wrote:
> On Dec 21, 2007 9:51 AM, Justin Bailey <jgbailey at gmail.com> wrote:
> > I think its [1..] which is building up the unevaluated thunk. Using
> > this definition of dropTest does not blow the stack:
> 
> It also works if you do [(1::Int) ..] !! n, but not with [(1::Integer) ..] !! n
> 
> Sounds like GHC is being smart about strictness for Ints, but doesn't
> know that Integer is equally strict.  If that's right, it's a bug in
> GHC.

It is a bug in GHC. From
http://darcs.haskell.org/packages/base/GHC/Enum.lhs

    enumFrom (I# x) = eftInt x maxInt#
        where I# maxInt# = maxInt
	-- Blarg: technically I guess enumFrom isn't strict!

...

eftInt x y | x ># y    = []
	   | otherwise = go x
	       where
		 go x = I# x : if x ==# y then [] else go (x +# 1#)