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From: jbn@lulea.trab.se (Johan Bengtsson)
Newsgroups: comp.std.c++
Subject: Re: Zero-length structures and pointer comparisons
Message-ID: <5358@holden.lulea.trab.se>
Date: 11 Dec 92 13:44:13 GMT
References: <1992Dec10.142408.28799@bcrka451.bnr.ca>
Organization: Telia Research AB, Aurorum 6, 951 75 Lulea, Sweden
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Stuart MacMartin (sjm@bcrki65.bnr.ca) wrote:
: In article <1992Dec10.051649.10282@jyu.fi> sakkinen@jyu.fi (Markku Sakkinen) writes:
: >
: >Second, the _identity_ of a persistent object in the database does not
: >change when the object is brought (or copied) to main memory.
: >The ordering is not supposed to be connected with the other
: >semantics of the objects, nor with their location in physical or
: >virtual memory (except as already dictated by the existing language
: >rules for array elements and class members, in C++).

: Thus the database
: will have to provide a routine, say ptrcmp(Handle,Handle) to compare the
: total ordering of two objects.  It could also provide ptrcmp(Handle,void *)
: and ptrcmp(void *,Handle), arbitrarily deciding that all C++ objects are
: less than all database objects, say.

Note that some OODBMS has the equivalent of
typedef void* Handle;

which I imagine slightly complicates things.

-- 
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