[Haskell-cafe] looking for optimization advice

[Simon Marlow]

> 
> data PackedString = PS !(ForeignPtr Word8) !Int !Int

A ForeignPtr is a sum type, so it can't be unboxed unfortunately.  This
is undoubtedly one cause of inefficiency in the code.

Depending on how you're using ForeignPtrs, you could possibly define a
specialiased kind of ForeignPtr that would be unboxable.  This would
require using low-level non-portable stuff though.  Are you using
mallocForeignPtr?  Or adding extra finalizers to ForeignPtrs?

Cheers,
	Simon