On Wed, Jan 24, 2007 at 01:14:45PM +0000, Simon Marlow wrote:

John Meacham wrote:

...

I would like to create a datatype that contains some memory managed by the GHC runtime, the natural fit is ByteArr#, however, in the common case, the ByteArr# won't actually have anything in it. would it be possible to have a single constant 'nullByteArr#'? I can't define a top level value of type ByteArr# and creating these values is in very performance critical code so I am not quite sure what to do. It would also be nice if byteArrContents# returned 'nullAddr#' for such byte arrays, but it is not a strict requirement.

I guess you could use nullByteArr# = (unsafeCoerce# True) - that shouldn't cause anything to go horribly wrong if you don't do any operations on it. If you want a way to tell whether a particular ByteArr# is nullByteArr# or not, then we'd have to elaborate the implementation of byteArrContents#. None of this is particularly hard, if I've understood it correctly.

Cool, if that works then it is good enough for me. I was worried that the garbage collector might do some type-based thing and get confused to see a thunk when it expects an unboxed array. John -- John Meacham - ⑆repetae.net⑆john⑈