[Haskell-cafe] Re: [Haskell] Re: Global Variables and IO
Keith.Wansbrough at cl.cam.ac.uk
Mon Nov 8 12:57:47 EST 2004
Adrian Hey writes:
> The problem is simple enough to restate for anyone who's interested.
> "Provide a simple reliable mechanism to ensure that in a given
> program run one particular top level IO operation cannot be executed
> more than once."
> > Can you give one concrete example of an "intended application
> > of oneShot", so that we can either propose a concrete Haskell
> > implementation of it, or agree that global variables really are necessary.
> Any C library which requires an explicit initialisation call before anything
> in that library can be used (common enough IME). Accidental re-initialisation
> (e.g. by two independent modules/libraries) will destroy any state currently
> be used by the libraries existing "clients".
Great, thanks, that's just what I was hoping for - I now see the
problem you're trying to address.
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