On Sun, May 3, 2009 at 6:11 PM, Ryan Ingram
So, I don't know what is causing your problem, but foo will not do what you want even with lazy ST.
That depends on what he wants to do. As long as nothing subsequent to the call to foo tries to read a reference, then foo is fine. For example, this works fine: bar r = do x <- readSTRef r writeSTRef $! x + 1 return x
take 10 $ runST (newSTRef 0 >>= \r -> sequence (repeat (bar r))) [0,1,2,3,4,5,6,7,8,9]
Does anyone know why the program just outputs <<loop>> when compiled under ghc 6.10.2, and runs perfectly fine under ghc 6.8.2? The program is compiled with --make and -O2
As I understand it, you get <<loop>> when the RTS detects a thunk
which depends on itself, which can happen if you're trying to do a
strict computation lazily.
I can't imagine why different versions of GHC would give different
results, though.
--
Dave Menendez