[Haskell-cafe] Re: [Haskell] Re: Global Variables and IO initializers

Keith Wansbrough 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.

--KW 8-)

More information about the Haskell-Cafe mailing list