[Haskell-cafe] Can't seem to get `par` working appropriately with lists

[Jules Bean]

Luke Andrew wrote:
>    import Control.Parallel
> 
>    fib1 n = if n == 0 then 0 else if n == 1 then 1 else fib1 (n-1) +
> fib1 (n-2)
>    fib2 n = if n == 0 then 0 else if n == 1 then 1 else fib2 (n-1) +
> fib2 (n-2)
> 
>    main = do print $ (fib2 37 `par` fib1 37) + (fib2 37)


"fib2 37" won't be shared.

You're telling ghc to calculate fib2 37 once, in parallel, throw it 
away, and then calculate it again.

Try:

let f1 = fib1 37
     f2 = fib2 37
in print $ (f2 `par` f1) + f2

Jules