[Haskell-cafe] REALLY simple STRef examples

[Chad Scherrer]

I've looked around at the various STRef examples out there, but still
nothing I write myself using this will work. I'm trying to figure out
how the s is escaping in really simple examples like

x = runST $ return 1

y = runST $ do {r <- newSTRef 1; readSTRef r}

Neither of these works in ghci - they both say

<interactive>:1:0:
    Inferred type is less polymorphic than expected
      Quantified type variable `s' escapes
      Expected type: ST s a -> b
      Inferred type: (forall s1. ST s1 a) -> a
    In the first argument of `($)', namely `runST'
    In the definition of `it':
       ...

I thought maybe I needed to replace 1 with (1 :: Int) so the state
representation didn't force the type, but it still gives the same
result.

Can someone point me to the simplest possible runST example that
actually works? Thanks!

-- 

Chad Scherrer

"Time flies like an arrow; fruit flies like a banana" -- Groucho Marx