On Mon, 2009-03-16 at 14:17 -0700, Jonathan Cast wrote:
On Mon, 2009-03-16 at 22:12 +0100, Henning Thielemann wrote:
On Sun, 15 Mar 2009, Claus Reinke wrote:
import Data.IORef import Control.Exception
main = do r <- newIORef 0 let v = undefined handle (\(ErrorCall _)->print "hi">>return 42) $ case f v of 0 -> return 0 n -> return (n - 1) y <- readIORef r print y
I don't see what this has to do with strictness. It's just the hacky "exception handling" which allows to "catch" programming errors.
And which I have a sneaking suspicion actually *is* `unsafe'. Or, at least, incapable of being given a compositional, continuous semantics.
See this paper: "A semantics for imprecise exceptions" http://research.microsoft.com/en-us/um/people/simonpj/papers/imprecise-exn.h... Basically if we can only catch exceptions in IO then it doesn't matter, it's just a little extra non-determinism and IO has plenty of that already. Duncan