Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!uakari.primate.wisc.edu!dogie.macc.wisc.edu!gatech!udel!rochester!pt.cs.cmu.edu!sei!firth
From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: comp.lang.misc
Subject: Re: :=
Message-ID: <4319@bd.sei.cmu.edu>
Date: 4 Oct 89 17:34:43 GMT
References: <1989Oct3.182931.518@jarvis.csri.toronto.edu> <6054@tekgvs.LABS.TEK.COM>
Reply-To: firth@sei.cmu.edu (Robert Firth)
Organization: Software Engineering Institute, Pittsburgh, PA
Lines: 25

In article <6054@tekgvs.LABS.TEK.COM> toma@tekgvs.LABS.TEK.COM (Tom Almy) writes:

>I personally would like to see the left arrow back. It makes more sense
>than colon equal...

The Algol-60 that people used at the Royal Military College still had the
back arrow in 1973; it was in the 64-character code of the ICL computers.
So, when we moved to PDP-11 (and, later, VAX-11), we simply kept it
and added ':=' as an alternative.  By changing the bitmap used by
our Versatex (TM) matrix printer, we made the ISO underscore look
like a back arrow, so those who hated ':=' could read the printed
copy of their code and feel happy.

The reason I dislike ':=' is purely practical: the two characters
are on different shifts, and when typing fast I tend to end up with
";=" or ":+" far too often.  For the same reason, I detest the
underscore as the break character in languages like Ada.  (There
is another reason to detest it - when faced with things like
"Text_IO.New_Line" the eye naturally groups the components by
following the physical separation, so "." is psychologically
more tightly binding than "_" and the actual lexis is counterintuitive.)

Unfortunately, it's probably too late to change back.  Though we
should surely use the impending change to ISO Latin-1 as a reason
to rethink some of the graphical symbols used in programming languages.