[Haskell-cafe] Re: [Haskell] Top Level <-

Yitzchak Gale gale at sefer.org
Wed Sep 3 07:12:39 EDT 2008

Ashley Yakeley wrote:
> Currently Data.Unique uses the "NOINLINE unsafePerformIO"
> hack to create its MVar. If hs-plugins duplicates that MVar,
> that's a bug in hs-plugins.

Sittampalam, Ganesh wrote:
> Also, the definition of NOINLINE in the report doesn't
> preclude copying both the MVar *and* its use sites,

Right. It would not be a bug in hs-plugins. That is the most
urgent problem right now.

It is nice to discuss various proposed new language
features. That is the way to solve the problem in
the long term.

But right now - there is no way to do this in Haskell at
all. The NOINLINE unsafePerformIO hack doesn't really
work. This is currently a major hole in Haskell in my

For the short term - can we *please* get an ONLYONCE
pragma that has the correct semantics?


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