Where did /= come from?

Where did /= come from?

[Programmer Dude]

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?)

-- 
|_ CJSonnack <Chris@Sonnack.com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ ___________________| Call: 1-800-DEV-NULL  |
|_____________________________________________|_______________________|



Opinions expressed herein are my own and may not represent those of my employer.

Re: Where did /= come from?

[Preben Randhol]

Programmer Dude wrote:
> 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?)

I don't know if it is the real reason, but the mathematical sign for not
equal is: =/=. That is a = with a / through it. I find the != symbol in C
completely confusing as ! is an exclamation mark so it sounds more like
EQUAL than not equal :-)

-- 
Preben Randhol  --------------------  http://www.pvv.org/~randhol
�.., chaos is found in greatest abundance wherever order is being
sought. It always defeats order, because it is better organized.�
                            -- Interesting Times, Terry Pratchett

Re: Where did /= come from?

[Programmer Dude]

Preben Randhol wrote:

>> I'm curious about its derivation or the reason behind the lexography.
>> (Perhaps a desire to use common keyboard characters?)
> 
> I don't know if it is the real reason, but the mathematical sign for not
> equal is: =/=. That is a = with a / through it.

Ah, that makes sense!

> I find the != symbol in C completely confusing as ! is an exclamation
> mark so it sounds more like EQUAL than not equal :-)

[grin] In my background I'm so used to thinking of 'bang' as 'not'
that makes perfect sense to me.  It just shows ta go ya!


> Preben Randhol  --------------------  http://www.pvv.org/~randhol
> �.., chaos is found in greatest abundance wherever order is being
> sought. It always defeats order, because it is better organized.�
>                             -- Interesting Times, Terry Pratchett

My very favorite author and modern philosopher!

-- 
|_ CJSonnack <Chris@Sonnack.com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ ___________________| Call: 1-800-DEV-NULL  |
|_____________________________________________|_______________________|



Opinions expressed herein are my own and may not represent those of my employer.

Re: Where did /= come from?

[Robert A Duff]

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

Re: Where did /= come from?

[Programmer Dude]

Robert A Duff wrote:

> It's as close as you can get to the normal maths symbol ("=" with a
> slash through it) in 7-bit Ascii...

That's two votes for it and none opposed.  The Ayes have it.
(Sorry, that time of year in America.)


> 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.

Sure.  Apples <> Oranges !!
       Apples <  Oranges ??

-- 
|_ CJSonnack <Chris@Sonnack.com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ ___________________| Call: 1-800-DEV-NULL  |
|_____________________________________________|_______________________|



Opinions expressed herein are my own and may not represent those of my employer.

Re: Where did /= come from?

[Matthew Baulch]

On Wed, 06 Nov 2002 10:12:59 +0000, Programmer Dude wrote:

> 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?)

I'm not advocating C when I say this, but != makes far more sense than /=
lexically speaking. In C, the Negative of a bool is retrieved with !foo.
In Ada, not foo. So I believe that K&R got it right using the != operator
for 'not equal'. Ada on the other hand doesn't use the ! operator and "not
equal" is too clumsy so it could be far worse than '/='.

Re: Where did /= come from?

[Preben Randhol]

Matthew Baulch wrote:
> 
> I'm not advocating C when I say this, but != makes far more sense than /=
> lexically speaking. In C, the Negative of a bool is retrieved with !foo.
> In Ada, not foo. So I believe that K&R got it right using the != operator
> for 'not equal'. Ada on the other hand doesn't use the ! operator and "not
> equal" is too clumsy so it could be far worse than '/='.

Well you can argue that they got it wrong when they chose ! in stead of
not and = instead of := and == in stead of = ;-)

-- 
Preben Randhol  --------------------  http://www.pvv.org/~randhol
�.., chaos is found in greatest abundance wherever order is being
sought. It always defeats order, because it is better organized.�
                            -- Interesting Times, Terry Pratchett

Re: Where did /= come from?

[Preben Randhol]

Programmer Dude wrote:
>> Preben Randhol  --------------------  http://www.pvv.org/~randhol
>> �.., chaos is found in greatest abundance wherever order is being
>> sought. It always defeats order, because it is better organized.�
>>                             -- Interesting Times, Terry Pratchett
> 
> My very favorite author and modern philosopher!

I don't find him a philosopher, I just found this quote to be sadly
true. ;-) On the other hand one could argue that since the entroy of the
universe is increasing one need to keep using energy to reduce the
entroy of say ones desk. :-)

-- 
Preben Randhol  --------------------  http://www.pvv.org/~randhol
�.., chaos is found in greatest abundance wherever order is being
sought. It always defeats order, because it is better organized.�
                            -- Interesting Times, Terry Pratchett

Re: Where did /= come from?

[David C. Hoos, Sr.]

The word is "entropy" not "entroy"
----- Original Message -----
From: "Preben Randhol" <randhol+news@pvv.org>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada.eu.org>
Sent: November 07, 2002 3:31 AM
Subject: Re: Where did /= come from?


> Programmer Dude wrote:
> >> Preben Randhol  --------------------  http://www.pvv.org/~randhol
> >> �.., chaos is found in greatest abundance wherever order is being
> >> sought. It always defeats order, because it is better organized.�
> >>                             -- Interesting Times, Terry Pratchett
> >
> > My very favorite author and modern philosopher!
>
> I don't find him a philosopher, I just found this quote to be sadly
> true. ;-) On the other hand one could argue that since the entroy of the
> universe is increasing one need to keep using energy to reduce the
> entroy of say ones desk. :-)
>
> --
> Preben Randhol  --------------------  http://www.pvv.org/~randhol
> �.., chaos is found in greatest abundance wherever order is being
> sought. It always defeats order, because it is better organized.�
>                             -- Interesting Times, Terry Pratchett
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada.eu.org
> http://ada.eu.org/mailman/listinfo/comp.lang.ada
>
>

Re: Where did /= come from?

[Preben Randhol]

David C. Hoos, Sr. wrote:
> The word is "entropy" not "entroy"

Hmm, how did I manage that typo twice ?

-- 
Preben Randhol ---------------------- http://www.pvv.org/~randhol/ --
+---+ "There was, I think, never any reason to  believe in any innate
| ! |  superiority of the male, except his superior muscle."
+---+      -- Bertrand Russell, Ideas That Have Harmed Mankind (1950)

Re: Where did /= come from?

[Ted Dennison]

"Matthew Baulch" <matt@greenroom.com.au> wrote in message news:<pan.2002.11.07.06.50.35.988084@greenroom.com.au>...

> I'm not advocating C when I say this, but != makes far more sense than /=
> lexically speaking. In C, the Negative of a bool is retrieved with !foo.

In C, that's a very true statement, for both the reason you mention,
and because "/=" is actually a valid shortcut division operator, as I
recently discovered to my sorrow.

In Ada, it is *not* a true statement.

> In Ada, not foo. So I believe that K&R got it right using the != operator
> for 'not equal'. Ada on the other hand doesn't use the ! operator and "not
> equal" is too clumsy so it could be far worse than '/='.

K&R certianly got it right for C. However, that decision was based on
a rotten foundation of using unnessecarily terse notation for the
concept of "not", for allowing a shortcut "division back into"
operator, and for allowing assignments to be value returning
statements themselves.

As you point out, Ada's operator is just fine for Ada.

Re: Where did /= come from?

[Robert A Duff]

"Matthew Baulch" <matt@greenroom.com.au> writes:

> I'm not advocating C when I say this, but != makes far more sense than /=
> lexically speaking. ...

And hundreds of years of mathematicians got it all wrong?
Lucky K&R came along to set them straight!  ;-)

- Bob

Re: Where did /= come from?

[Frank J. Lhota]

For C to be consistent,

        a == b
    and
        a != b

should be equivalent to

        a = ( (a) = (b) )
    and
        a = ( (a) ! (b) )

respectively. Of course, C has not defined a binary "!" operator yet...

Re: Where did /= come from?

[Vinzent Hoefler]

"Matthew Baulch" <matt@greenroom.com.au> wrote:

> In C, the Negative of a bool is retrieved with !foo.

Well, because C has no "bool" in the sense of Boolean variables, this
is rather irrelevant.

The "!" probably was literally meant as "not" but does not really do
it, it just acts like a "compare with zero", simulating a Boolean. :-)

So "!=" does not make sense from this point of view. One could argue,
its just the best "visual" replacement they could get for a "/=" what
could not be used because it was already meant to be a complete
different thing. ;-)


Vinzent.

Re: Where did /= come from?

[Programmer Dude]

Preben Randhol wrote:

>>>                             -- Interesting Times, Terry Pratchett
>>
>> My very favorite author and modern philosopher!
> 
> I don't find him a philosopher, I just found this quote to be sadly
> true. ;-)

So many of his quotes are true (sadly or otherwise).  That's what
makes him (in my mind) a philosopher.  I think he truly is an acute
observer and reporter of the human condition.

Obviously, YMMV.  ;-)

-- 
|_ CJSonnack <Chris@Sonnack.com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ ___________________| Call: 1-800-DEV-NULL  |
|_____________________________________________|_______________________|



Opinions expressed herein are my own and may not represent those of my employer.

Re: Where did /= come from?

[Programmer Dude]

"Frank J. Lhota" wrote:

> For C to be consistent,
> 
>         a == b
>     and
>         a != b
> 
> should be equivalent to
> 
>         a = ( (a) = (b) )
>     and
>         a = ( (a) ! (b) )

That's funny!  ;-)

> Of course, C has not defined a binary "!" operator yet...

What about the compliment operator: ~

-- 
|_ CJSonnack <Chris@Sonnack.com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ ___________________| Call: 1-800-DEV-NULL  |
|_____________________________________________|_______________________|



Opinions expressed herein are my own and may not represent those of my employer.

Re: Where did /= come from?

[news.bctel.net]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1130 bytes --]

I think Ada could be more consistent regarding "/=".
consider following invariant expressed in C and Ada
C: !(A==B) same as (A != B)
Ada: not (A = B), but (A not = B) is incorrect syntax.

Alexei.

"Preben Randhol" <randhol+news@pvv.org> wrote in message
news:slrnaskc44.rf.randhol+news@kiuk0152.chembio.ntnu.no...
> Matthew Baulch wrote:
> >
> > I'm not advocating C when I say this, but != makes far more sense than
/=
> > lexically speaking. In C, the Negative of a bool is retrieved with !foo.
> > In Ada, not foo. So I believe that K&R got it right using the !=
operator
> > for 'not equal'. Ada on the other hand doesn't use the ! operator and
"not
> > equal" is too clumsy so it could be far worse than '/='.
>
> Well you can argue that they got it wrong when they chose ! in stead of
> not and = instead of := and == in stead of = ;-)
>
> --
> Preben Randhol  --------------------  http://www.pvv.org/~randhol
> �.., chaos is found in greatest abundance wherever order is being
> sought. It always defeats order, because it is better organized.�
>                             -- Interesting Times, Terry Pratchett

Re: Where did /= come from?

[Preben Randhol]

Programmer Dude wrote:
> So many of his quotes are true (sadly or otherwise).  That's what
> makes him (in my mind) a philosopher.

Nah, that would make an astologist a philosopher.

-- 
Preben Randhol ------------------------ http://www.pvv.org/~randhol/ --
�There are three things you can do to a woman. You can love her, suffer
 for her, or turn her into literature.�  - Justine, by Lawrence Durrell

Re: Where did /= come from?

[Preben Randhol]

news.bctel.net wrote:
> I think Ada could be more consistent regarding "/=".
> consider following invariant expressed in C and Ada

No, because IMHO that reduces the readability.

-- 
Preben Randhol ------------------------ http://www.pvv.org/~randhol/ --
�There are three things you can do to a woman. You can love her, suffer
 for her, or turn her into literature.�  - Justine, by Lawrence Durrell

Re: Where did /= come from?

[Preben Randhol]

Preben Randhol wrote:
> Programmer Dude wrote:
>> So many of his quotes are true (sadly or otherwise).  That's what
>> makes him (in my mind) a philosopher.
> 
> Nah, that would make an astologist a philosopher.

I mean it doesn't qualify for being a philosopher. An astrologist just
says a bunch of general bullshit that most people can relate to and then
they think "*WOW* this is how it is". :-)

Read the Dirk Gently books by Douglas Adams if you haven't. They are
great fun.

-- 
Preben Randhol ------------------------ http://www.pvv.org/~randhol/ --
�There are three things you can do to a woman. You can love her, suffer
 for her, or turn her into literature.�  - Justine, by Lawrence Durrell

Re: Where did /= come from?

[Frank J. Lhota]

Maybe this is why C / C++ programmers dislike the ":=" symbol for
assignment. They are bound to think that

    a := b

is equivalent to

    a = (a) : (b)

and the right hand side is missing the "cond ?" prefix.

Re: Where did /= come from?

[Programmer Dude]

Preben Randhol wrote:

>>> So many of [Terry Pratchett's] quotes are true (sadly or otherwise).
>>> That's what makes him (in my mind) a philosopher.
>>
>> Nah, that would make an astologist a philosopher.
> 
> I mean it doesn't qualify for being a philosopher. An astrologist just
> says a bunch of general bullshit that most people can relate to and then
> they think "*WOW* this is how it is". :-)

I see quite a difference between Pratchett and an astrologist, but I
agree overall.  That's why I said (in my mind).  And, in fact, "acute,
cogent and humorous reporter of the human condition" might be a better
term.  ;-)

> Read the Dirk Gently books by Douglas Adams if you haven't. They are
> great fun.

They were, but I liked HITCHHIKER better.  Few books have quite so many
delicious quotes.

-- 
|_ CJSonnack <Chris@Sonnack.com> _____________| How's my programming? |
|_ http://www.Sonnack.com/ ___________________| Call: 1-800-DEV-NULL  |
|_____________________________________________|_______________________|



Opinions expressed herein are my own and may not represent those of my employer.