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Hi,

For the following error:

Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize -RTS' to increase it.

I want to find out the culprit function and rewrite it tail-recursively. Is there a way to find out which function is causing this error other than reviewing the code manually?

I'd like to point out that a stack-space overflow in Haskell isn't quite the same thing as in other functional languages. In particular, it's possible for tail-recursive functions to overflow the stack because of laziness. Consider this tail-recursive sum function:

trSum :: [Int] -> Int trSum l = go 0 l where go acc [] = acc go acc (x:xs) = go (acc+x) xs

It's tail-recursive. But if you enter this in ghci and run it, you'll find that it uses increasing stack space, and will likely cause a stack overflow for large enough inputs. The problem is that the accumulator 'acc' isn't strict and builds up a thunk of the form: 0+n1+n2+...+nn The solution is to add strictness. For this example, a '!' on the accumulator will do. GHC will sometimes spot cases where extra strictness is helpful (it'll figure this one out when compiled with -O), but it often needs help. I'd recommend Edward Yang's series of blog posts about debugging, space leaks, and the Haskell heap. One useful article is http://blog.ezyang.com/2011/05/anatomy-of-a-thunk-leak/ , but you may want to start at the beginning of the heap series. John L.