[Haskell-cafe] ST not strict enough?

[Daniel Fischer]

On Friday 18 November 2011, 11:18:33, Yves Parès wrote:
> Instead of rewriting modifySTRef, why not just do :
> 
> modifySTRef counter (\x -> let y = x+1 in y `seq` y)
> 
> Is there a problem with that?

Yes, y `seq` y is precisely the same as y.

a `seq` b means whenever evaluation of b is demanded, also evaluate a (to 
WHNF).
So y `seq` y ~> whenever evaluation of y is demanded, also evaluate y.