🚀 go-pugleaf

jimad@microsoft.com (Jim Adcock) writes:

>I think some flavor of "ptrcmp" makes sense on those implementations that
>support casting pointers to integrals and back, and probably doesn't make
>sense on those implementations that don't support the pointer/integral casts.
>
>In either case, I would ask what kind of sense it makes to write a "standard"
>that *requires* a certain behavior of *some* implementation but doesn't
>*require* that behavior of *all* implementations?  How do you justify such
>a dichotomy?

ptrcmp() is intended to be universal, ie. required of *all* implementations.

>Such would be the proper designation, IMHO, for both the bidi pointer/integral
>cast, and for the proposed "ptrcmp" macro.  Then, on Lisp machines, or 
>C++ OODBMS's or whatever systens would find the total ordering 
>practically unsupportable in their environment [...]

Why would ptrcmp() be practically unsupportable in these environments?
OODBMS's maintain an object identity for each object, so it should be
possible to base a total ordering on this object identity. I don't see
the problems. What makes it difficult for Lisp machines? Are efficient
BTrees and such-like genuinely impossible on such machines?

>In any case, "ptrcmp" would be a misnomer, because what is being compared
>is *not* pointers, but rather the underlying *assumed* implementation of 
>pointers using machine addresses.  The correct name might be something like 
>"addrcmp" then, so as to not further confuse programmers on the difference
>between language and implementation.

The function should be named after its interface, not its implementation.
The function takes two (void *) _pointers_, and returns an integer which
is meant to be a comparison of those pointers according to some total
ordering.
Whether it is implemented by comparing addresses or by sending mail to
the Usenet Oracle and waiting for a reply is not relevant.

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