Re: [Haskell-cafe] Exception handling when using STUArray

On Sat, 8 Mar 2008, Denis Bueno wrote:

On Sat, Mar 8, 2008 at 12:29 AM, Xiao-Yong Jin wrote:

...

I'm using STUArray in some of my time critical number crunching code. I would like to know some way to catch the exceptions raised in the ST monad, ie. ArrayException.

I am also using STUArray from some time-critical code; however, I don't deal with ArrayException, or any exceptions for that matter. What besides an out-of-bounds read or write might throw an ArrayException? If it is out-of-bounds reading or writing, surely that indicates a bug in your program that you'd rather fix than catch the exception, no?

Another instance of mixing up exceptions and errors in the Haskell libraries. http://www.haskell.org/haskellwiki/Error http://www.haskell.org/haskellwiki/Exception

Also, if you're using GHC, note that the ArrayException documentation says:

"(NOTE: GHC currently does not throw ArrayExceptions)."

...

Looking through the Control.Exception module, I understand that those functions can only be used within IO monad. So

This isn't quite true, if I understand what you mean. The function throw can be used from any code (http://haskell.org/ghc/docs/latest/html/libraries/base/Control-Exception.htm...). But you must catch exceptions in the IO monad.

...

my question is, what the best way to do exception handling in STUArray is. Plus, it would be helpful if I can also raise an exception in ST monad, but how?

I think what I noted in the last paragraph solves this problem.