[Haskell-cafe] Why doesn't this work?
alfonso.acosta at gmail.com
Sun Aug 24 09:36:52 EDT 2008
I haven't tried to run the code, but my first bet is that, due to the
rank-2 polymorphism of ST, you should use parenthesis instead of $ in
the case of runST.
On Sun, Aug 24, 2008 at 3:25 PM, Andrew Coppin
<andrewcoppin at btinternet.com> wrote:
> colour_grid :: (Particle -> IO ()) -> Grid ph -> IO ()
> colour_grid fn g = sequence_ $ runST $ do
> ps <- grid_coords g
> (\pix -> do
> particle <- read_grid g pix
> return $ fn particle
> When I attempt to run this, GHCi just gives me a very cryptic type checker
> error. I can't figure out what's wrong here. As far as I can tell, this
> should run...
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