Dilemma: DiffArray non-performance vs STArray non-readability

[Claus Reinke]

>> Should I add a ticket?
> 
> Sounds good - and if you could attach a small example showing how Array
> is faster that would be helpful too.

Ok, ticket is http://hackage.haskell.org/trac/ghc/ticket/2727 .

Hope I got the example right - the effect is clear, but with "functional"
DiffArray, it is way too easy to lose single-threadedness.

In addition to the basic slowness issue, it appears there has been a
serious regression in the area (handling of $! perhaps?) since 6.4.1.

Claus