On Fri, Oct 09, 2009 at 01:27:57PM -0400, David Menendez wrote:
> On Fri, Oct 9, 2009 at 11:12 AM, Felipe Lessa <felipe.le...@gmail.com> wrote:
> > That's really nice, Oleg, thanks! I just wanted to comment that
> > I'd prefer to write
> >
> > share :: IO a -> IO (IO a)
> > share m = mdo r <- newIORef (do x <- m
> > writeIORef r (return x)
> > return x)
> > return (readIORef r >>= id)
> >
> > which unfortunately needs {-# LANGUAGE RecursiveDo #-} or
> > some ugliness from mfix
> >
> > share :: IO a -> IO (IO a)
> > share m = do r <- mfix $ \r -> newIORef (do x <- m
> > writeIORef r (return x)
> > return x)
> > return (readIORef r >>= id)
> >
>
> Alternatively,
>
> share m = do
> r <- newIORef undefined
> writeIORef r $ do
> x <- m
> writeIORef r (return x)
> return x
> return $ readIORef r >>= id
>
> Which is basically the same as your version, but only needs one IORef.
Hmmm, but my version also needs only one IORef, right? In fact I
first wrote the same code as yours but I've frowned upon the need
of having that 'undefined' and an extra 'writeIORef'.
Thanks,
--
Felipe.
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