Path: utzoo!mnetor!uunet!husc6!bloom-beacon!gatech!ufcsv!codas!burl!clyde!ima!haddock!karl
From: karl@haddock.ISC.COM (Karl Heuer)
Newsgroups: comp.lang.misc
Subject: Re: History of := (was: == vs =)
Message-ID: <2375@haddock.ISC.COM>
Date: 24 Jan 88 20:07:12 GMT
References: <2337@haddock.ISC.COM> <51300003@uxe.cso.uiuc.edu>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Boston
Lines: 18

In article <51300003@uxe.cso.uiuc.edu> hirchert@uxe.cso.uiuc.edu writes:
>I was a math major in college and I can't ever remember seeing := used in a
>mathematical rather than computer science context.

I don't see it used very often, but it means "is defined to be equal to".  The
opposite symbol "=:", which means that the RHS is the term being defined, is
sometimes used when it's more convenient (as in A = B = C =: D, which might
mean that A can be reduced to B and thence to C, and that we will henceforth
refer to this expression by D).

>If there is a current mathematical usage of this symbol, are you sure that it
>didn't derive from the computer usage?

No, I'm not certain.  I'm guessing, based on the differing semantics, that
it's more likely to have migrated the other way.  And where I've seen it used
this way in Mathematics, there was no computer context.

Karl W. Z. Heuer (ima!haddock!karl or karl@haddock.isc.com), The Walking Lint