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From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: comp.mail.uucp
Subject: Re: Say "preference" rather than "precedence" in network addresses (was: Re: UUCP map changes (important!))
Message-ID: <860@mcgill-vision.UUCP>
Date: Sat, 15-Aug-87 00:27:07 EDT
Article-I.D.: mcgill-v.860
Posted: Sat Aug 15 00:27:07 1987
Date-Received: Wed, 26-Aug-87 06:17:18 EDT
References: <112@stargate.UUCP> <908@bsu-cs.UUCP>
Organization: McGill University, Montreal
Lines: 41

In article <908@bsu-cs.UUCP>, dhesi@bsu-cs.UUCP (Rahul Dhesi) writes:
> In article <112@stargate.UUCP> pleasant@rutgers.EDU (Mel Pleasant) writes:
>> RFC976 defines the @ network character as having precedence over the
>> bang (!) when both appear in mixed mode addresses.

> The quoted use of the term "precedence" is frequently used to mean
> that when a mailer sees a construct of the form a!b@c it groups it as
> (a!b)@c rather than a!(b@c).

Almost invariably so used, when discussing mail addresses.  (Nor is it
likely to change, as I shall explain.)

> This is an unfortunate use.  Consider the statement:

>      My algebra book defines the * arithmetic character as having
>      precedence over the plus (+) in arithmetic expressions.

> This, by analogy with the previous quote, would imply that a+b*c
> would be grouped as (a+b)*c rather than as a+(b*c), which is wrong.

Heavens no.

You have asked a tough one.  Both uses are very natural, but it is
difficult to say exactly why, when they are so obviously opposite in
certain senses.  But I'll have a stab at it anyway.

The use of `precedence' in both cases means that the higher-precedence
operator binds tighter, that is, it is handled first.  Parentheses
indicate that the pieces within them are to be taken as a unit with
respect to whatever operations appear outside the parentheses.  The
point of difference is that for arithmetic, this means that the
expression inside parentheses must be evaluated first, while in mail
addresses, treatment as a unit means that the thing being treated as a
unit must have its handling deferred until later, possibly on some
other machine.

Clear?  I didn't really expect so, but I have to try....

					der Mouse

				(mouse@mcgill-vision.uucp)