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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: Where did /= come from?
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cjsonnack@mmm.com (Programmer Dude) writes:

> I'm learning Ada (installed GNAT and AdaGIDE last week, wrote Hello, World).
> 
> I was somewhat bemused to stumble on Ada's version of "not equals": /=
> 
> I'm curious about its derivation or the reason behind the lexography.
> (Perhaps a desire to use common keyboard characters?)

It's as close as you can get to the normal maths symbol ("=" with a
slash through it) in 7-bit Ascii (which was the standard when Ada was
designed).  I seem to recall a suggestion in the Ada 83 Rationale
suggesting that programs for printing Ada code could print it as
"/", backspace, "=", thus producing a maths not-equal sign.

Nowadays there are programs that print "/=" and "<=" and so forth in the
proper maths way.  For example, a2ps has modes for Ada, C, etc, that can
do that sort of thing.

Ada is descended from Pascal, which uses "<>" for not-equal.
That's pretty ugly, IMHO, and I'm glad Ada didn't mimic it.
For integers, "less than or greater than" is the same as "not equal",
but many types have a not-equal operator but no less-than, etc.

- Bob