Why isn't there a logical XOR operator?

[Christopher Benson-Manica]

Of course one can get the effect with appropriate use of existing
operators, but a ^^ operator would make for nice symmetry (as well as
useful to me in something I'm working on). Am I the only one who
would find it useful?

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Joona I Palaste]

Christopher Benson-Manica <at***@nospam.c yberspace.org> scribbled the following:

Of course one can get the effect with appropriate use of existing
operators, but a ^^ operator would make for nice symmetry (as well as
useful to me in something I'm working on). Am I the only one who
would find it useful?

You mean an operator that returns 1 if exactly one of its operands is
nonzero, and 0 otherwise? Yes, that would be useful. But forget about
the short-circuit semantics. Think about it and you'll see why.

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/

[Joona I Palaste]

Joona I Palaste <pa*****@cc.hel sinki.fi> scribbled the following:

Christopher Benson-Manica <at***@nospam.c yberspace.org> scribbled the following:

Of course one can get the effect with appropriate use of existing
operators, but a ^^ operator would make for nice symmetry (as well as
useful to me in something I'm working on). Am I the only one who
would find it useful?

You mean an operator that returns 1 if exactly one of its operands is
nonzero, and 0 otherwise? Yes, that would be useful. But forget about
the short-circuit semantics. Think about it and you'll see why.

Also if there were an unary ^ operator, we could write Japanese smileys
into our code. For example:
sashimi ^=^ kawaii;

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"War! Huh! Good God, y'all! What is it good for? We asked Mayor Quimby."
- Kent Brockman

[nrk]

Christopher Benson-Manica wrote:

Of course one can get the effect with appropriate use of existing
operators, but a ^^ operator would make for nice symmetry (as well as
useful to me in something I'm working on). Am I the only one who
would find it useful?

If you write your conditions to be all logical (that is avoid the if ( x )
style idioms), then using the existing xor operator would achieve exactly
the same thing as your proposed ^^, wouldn't it? I mean, there can be no
short-circuit evaluation of an xor operator.

-nrk.
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[Christopher Benson-Manica]

Joona I Palaste <pa*****@cc.hel sinki.fi> spoke thus:

You mean an operator that returns 1 if exactly one of its operands is
nonzero, and 0 otherwise? Yes, that would be useful. But forget about
the short-circuit semantics. Think about it and you'll see why.

Hm, that's true. A ^^ B would have to evaluate A and B... I hadn't
thought of that, and I suppose that was a greater good than &/&&
and |/|| symmetry. Interesting.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[Christopher Benson-Manica]

Joona I Palaste <pa*****@cc.hel sinki.fi> spoke thus:

Also if there were an unary ^ operator, we could write Japanese smileys
into our code. For example:
sashimi ^=^ kawaii;

This assumes, of course, that C authors are familiar with the Japanese
emoticon paradigm ^_~

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cybers pace.org | don't, I need to know. Flames welcome.

[xarax]

"nrk" <ra*********@de vnull.verizon.n et> wrote in message
news:ma******** *****@nwrddc01. gnilink.net...

Christopher Benson-Manica wrote:

Of course one can get the effect with appropriate use of existing
operators, but a ^^ operator would make for nice symmetry (as well as
useful to me in something I'm working on). Am I the only one who
would find it useful?

If you write your conditions to be all logical (that is avoid the if ( x )
style idioms), then using the existing xor operator would achieve exactly
the same thing as your proposed ^^, wouldn't it? I mean, there can be no
short-circuit evaluation of an xor operator.

(a ^^ b) would be something like ((!!a) != (!!b)). Could
be macrotized rather easily? Could the double bang be
reduced to a single bang on each side?

[Joona I Palaste]

xarax <xa***@email.co m> scribbled the following:

"nrk" <ra*********@de vnull.verizon.n et> wrote in message
news:ma******** *****@nwrddc01. gnilink.net...

Christopher Benson-Manica wrote:

> Of course one can get the effect with appropriate use of existing
> operators, but a ^^ operator would make for nice symmetry (as well as
> useful to me in something I'm working on). Am I the only one who
> would find it useful?
> If you write your conditions to be all logical (that is avoid the if ( x )
style idioms), then using the existing xor operator would achieve exactly
the same thing as your proposed ^^, wouldn't it? I mean, there can be no
short-circuit evaluation of an xor operator.

(a ^^ b) would be something like ((!!a) != (!!b)). Could
be macrotized rather easily? Could the double bang be
reduced to a single bang on each side?

Yes, ((!!a) != (!!b)) is equivalent to ((!a) != (!b)).

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"It was, er, quite bookish."
- Horace Boothroyd

[CBFalconer]

Christopher Benson-Manica wrote:

Of course one can get the effect with appropriate use of existing
operators, but a ^^ operator would make for nice symmetry (as well as
useful to me in something I'm working on). Am I the only one who
would find it useful?

if (!!a ^ !!b) ....

c = !!a ^ !!b;

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[nrk]

xarax wrote:

"nrk" <ra*********@de vnull.verizon.n et> wrote in message
news:ma******** *****@nwrddc01. gnilink.net...

Christopher Benson-Manica wrote:

> Of course one can get the effect with appropriate use of existing
> operators, but a ^^ operator would make for nice symmetry (as well as
> useful to me in something I'm working on). Am I the only one who
> would find it useful?
>

If you write your conditions to be all logical (that is avoid the if ( x
) style idioms), then using the existing xor operator would achieve
exactly
the same thing as your proposed ^^, wouldn't it? I mean, there can be no
short-circuit evaluation of an xor operator.

(a ^^ b) would be something like ((!!a) != (!!b)). Could
be macrotized rather easily? Could the double bang be
reduced to a single bang on each side?

Yes, as x xor y is the same as x' xor y'. However, while this is pretty
neat, I think it makes the code harder to comprehend than using a straight
xor operation on the logical conditions (maybe its me that gets confused
when seeing negation all over the place).

And for those who believe that the xor shouldn't be used in combining
logical conditions, there is one situation where I have found this to be
eminently useful: when processing command line arguments where two
different options are mutually incompatible, but atleast one of them must
have been specified.

-nrk.

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