[Haskell-cafe] Re: ANNOUNCE: protocol-buffers-0.2.9 for Haskell is ready

Bulat Ziganshin bulat.ziganshin at gmail.com
Mon Sep 22 08:15:50 EDT 2008

Hello Chris,

Monday, September 22, 2008, 2:48:16 PM, you wrote:

> used a very unreliable trick.  And the "use castToSTUArray" suggested
> alternative is a really poor one since I am not using arrays at all.

castToSTUArray does the same as your code, only in ST monad so you can
skip unsafePerformIO trick

if you dn't know, ST is a subset of IO monad with a limited set of
operations guaranteed to not have side-effects. so,

cvt x = unsafePerformIO $
        do alloca $ \place -> do
           poke place x
           peek place


cvt x = runST $
        do place <- newArray (0,1)
           writeArray place 0 x
           readArray place 0

generates almost the same code (the only difference is kind of memory

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

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