🚀 go-pugleaf

In article <5347@holden.lulea.trab.se> jbn@lulea.trab.se (Johan Bengtsson) writes:
>Dag Bruck (dag@seldon.control.lth.se) wrote:
>: 	p == q   <=>   ptrcmp(p,q) == 0
>
>: 	p != q   <=>   ptrcmp(p,q) != 0
>
>: 	ptrcmp(p,q) < 0   <=>   ptrcmp(q,p) > 0
>
>I think ptrcmp() is a good way to resolve this issue.
>
>There is only one possible remaining weakness (I think):

	I disagree, but anyhow ...
>
>Any environment that relies on pointer translation (swizzling) to
>transport objects between executing processes will have difficulty
>maintaining a common total ordering for the pointers (IDs) of
>objects within those processes (Jim Adcock pointed this out).
>Examples include OODBMS and distributed systems.  Code relying
>on ptrcmp() may be unportable to those environments.
>
>Should those environments be required to (somehow) provide special
>ptrcmp() functions, that look at some object ID (not memory address)?
>What if a program uses more than one pointer swizzling scheme (e.g.
>distributing some objects over communication channels, and storing other
>objects in an OODBMS)?  Is it the users job to provide the ordering
>between those different object spaces?
>
>Anyone have a good solution for this?
>
	Yes. First look at ==. It is already flawed. The rules
must be rewritten so that == has the given semantics only
in 'domestic' cases. The results of == can be implementation
defined in any cases the pointers are not derived by
'ordinary' operations. That lets OODBMS off the hook.

	The same solution can be applied to ptrcmp now.

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