[Haskell-cafe] Plug space leak with seq. How?

[Alexey Khudyakov]

>
> forever a   = a>>  forever a
>
> doesn't tie to itself without optimisations, so my guess is that it gets
> expanded when you run/eval/execState it in ghci, building the thunk
>
> a>>  a>>  a>>  a>>  ...
>
> If you define
>
> forever' a = let a' = a>>  a' in a'
>
> the variant using forever' runs in constant space in ghci.
> This, like the explicit recursion, builds a cyclic structure, hence avoids
> the leak.

I see. It's difficult to reason about space complexity in presence of 
optimizer.