[Haskell-cafe] Stack overflow while programming imperatively

Hey list. I was recently fixing a space leak by dropping down to imperative programming in a section of my code, when it started developing space leaks of its own. I found the problem though - it was my "for loop": http://hpaste.org/65514 Can anyone provide suggestions on why that stack overflows? It seems ridiculously tail recursive. I tried to do it more haskell-like with http://hpaste.org/65517, but it was still spending 75% of its time in GC. Is there any way to write such a loop with ~100% productivity? I don't think there should be _any_ garbage generated, as all values may be stack allocated. Is this a performance regression in GHC? Thanks, - clark