Chaddaï Fouché wrote:
2007/9/26, Adrian Hey <[EMAIL PROTECTED]>:
Chaddaï Fouché wrote:
There can't be alternatives, unsafeIO throw by the window most
guarantee that Haskell can give you and you have to provide them
yourself (with a proof of this part of your program), but it's
inherent to the nature of the beast, it's what it do !
What about ..
http://www.haskell.org/haskellwiki/Top_level_mutable_state
This as unsafe a use of unsafePerformIO as you'll ever find, but
necessary for real IO libs.
I'm not arguing that there aren't specific current usage of
unsafePerformIO that could be better formalized (there are), I'm
saying that you can't design an alternative to unsafePerformIO which
cover all its applications but stay safer. What we can do with
unsafePerformIO is inherently unsafe, even though you can obtain safe
results with it (and in some of those use-case, a restricted version
of unsafePerformIO could be used and would be safer).
In your original post you appear to be making the usual argument about
proof obligations and the possibility that unsafePerformIO can be used
safely, despite the name (and should only be used this way). I was
simply pointing out that there is at least one common use of
unsafePerformIO for which this isn't possible (and there is currently
no safe alternative).
Regards
--
Adrian Hey
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