[Haskell-cafe] Re: Fast Mutable Variables for the IO and ST monads

[oleg at pobox.com]

Simon Marlow wrote:
> I suggest you follow the same scheme as the unboxed array types, and
> have IOURef/STURef types, parameterised over the element type.  Of
> course, we should have instances for all of the primitive numeric types
> plus Ptr, ForeignPtr, StablePtr, Bool.

Perhaps it may be worth to introduce a class Unpackable as described
at the end of
  http://www.haskell.org/pipermail/haskell-cafe/2004-July/006400.html

so we may define STUArray as an instance of MArray, and other similar
unpackable things easier?