[Haskell-cafe] stack overflow when using ST monad

[Gregory Wright]

Hi Bulat!

On Aug 24, 2006, at 1:07 PM, Bulat Ziganshin wrote:

> Hello Brian,
>
> Thursday, August 24, 2006, 4:16:41 PM, you wrote:
>
>> I would make all the fields strict here, to be sure that no  
>> lazyness can
>> creep about unseen eg:
>
>>      data Tag s = Tag {
>>          tagID :: !Int,
>>          state :: !(STRef s TagState),
>>          count :: !(STRef s Integer)
>>    }
>
> perhaps better:
>
>       data Tag s = Tag {
>           tagID :: !Int,
>           state :: STRef s !TagState,
>           count :: STRef s !Integer
>     }
>
> although i don't even sure that this will compile (in this case we can
> request it as wishful feature). in theory, this should allow to omit
> '$!' from writeRef calls
>

Alas, at the moment the last gives (in ghc-6.4.2),

     Unexpected strictness annotation: !TagState
     In the data type declaration for `Tag'
Failed, modules loaded: none.
Prelude>


> also, one can implement strict write operations:
>
> writeRef r x = writeSTRef r $! x
>
> or use my unboxed references (but not with Integer) -
> http://haskell.org/haskellwiki/Library/ArrayRef
>

I will look at this. Thanks!

Best Wishes,
Greg

>
> -- 
> Best regards,
>  Bulat                            mailto:Bulat.Ziganshin at gmail.com
>
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