x = 0; x += ++x + x++; x == 4?

[Christian Johannes Charbula]

Hi,

is this result defined by the standard?

I'm just in a small "fight" with some workmates on this topic. So an
answer from more involved people could help.

Regards,
Christian

[Victor Bazarov]

Re: x = 0; x += ++x + x++; x == 4?

Christian Johannes Charbula wrote:

is this result defined by the standard?

No. The second statement contains the expression in which the rules
are broken. See the Standard, [expr]/4.

I'm just in a small "fight" with some workmates on this topic. So an
answer from more involved people could help.

Never fight your workmates. It's detrimental to your career.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Johannes Bauer]

Re: x = 0; x += ++x + x++; x == 4?

Pete Becker schrieb:

A more important question, though, is "who cares?" Is it really
worhwhile spending time talking about the hypothetical meaning of an
expression that should never appear in real-world code? Even under
Java's rules, where the result is well defined, the code is abominable.

Exactly, I fully second that. I do not understand at all why this exact
question comes up in this group (and in comp.lang.c, too, BTW) every few
days. Kind of annoying. You should think people have more important
problems.

Regards,
Johannes

--
"PS: Ein Realname wäre nett. Ich selbst nutze nur keinen, weil mich die
meisten hier bereits mit Namen kennen." -- Markus Gronotte aka Makus /
Kosst Amojan / maqqusz / Mr. G / Ferdinand Simpson / Quartillia
Rosenberg in dse <45608268$0$571 9$9b4e6d93@news spool3.arcor-online.net>

[Victor Bazarov]

Re: x = 0; x += ++x + x++; x == 4?

Johannes Bauer wrote:

Pete Becker schrieb:
>

>A more important question, though, is "who cares?" Is it really
>worhwhile spending time talking about the hypothetical meaning of an
>expression that should never appear in real-world code? Even under
>Java's rules, where the result is well defined, the code is
>abominable.

>
Exactly, I fully second that. I do not understand at all why this
exact question comes up in this group (and in comp.lang.c, too, BTW)
every few days. Kind of annoying. You should think people have more
important problems.

Aw, those grown-ups and their "more important problems"! When
will they understand? <g>

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Johannes Bauer]

Re: x = 0; x += ++x + x++; x == 4?

Victor Bazarov schrieb:

>Exactly, I fully second that. I do not understand at all why this
>exact question comes up in this group (and in comp.lang.c, too, BTW)
>every few days. Kind of annoying. You should think people have more
>important problems.

>
Aw, those grown-ups and their "more important problems"! When
will they understand? <g>

No, no, that's not how I meant it and from the grin I take it you
undertood me correctly. However, I believe that there are *dozens* of
really interesting, complex, real-world problems C++ provides - yet some
people get hung with totally arfificial problems which always boils down
to some definition in the standard - that's pretty boring :-)

Regards,
Johannes

--
"PS: Ein Realname wäre nett. Ich selbst nutze nur keinen, weil mich die
meisten hier bereits mit Namen kennen." -- Markus Gronotte aka Makus /
Kosst Amojan / maqqusz / Mr. G / Ferdinand Simpson / Quartillia
Rosenberg in dse <45608268$0$571 9$9b4e6d93@news spool3.arcor-online.net>

[Juha Nieminen]

Re: x = 0; x += ++x + x++; x == 4?

Christian Johannes Charbula wrote:

is this result defined by the standard?

What result?

It's customary to write a complete question in the body of your post.
The subject line is only a short introduction to the contents of your
post, not the contents themselves. The post should be understandable
even without the subject line.

[Andrey Tarasevich]

Re: x = 0; x += ++x + x++; x == 4?

James Kanze wrote:

...

>Yes, but the original question was not about the "behavior", but about
>the "result". While the OP didn't specify what exactly he meant by
>"result" (probably the result of 'x == 4' expression), for many natural
>interpretation s of the term it is possible to come up with operator
>definitions, which will produce a well defined "result" even though the
>overall "behavior" is not specified.

>
It's possible,

That's exactly what I said. It is possible.

but anyone who overloads the given operators with
definitions so that such a result is guaranteed should be hung
and shot.

Considering that this discussion is centered around what essentially is
a basic C++ _puzzle_, not a piece of real-life code, the above statement
is utterly irrelevant.

With any reasonable overloading of the operators (for
a user defined type for which such operators would make sense),
the result is unspecified.

This statement is based on some undefinable ideas of what "reasonable ".
I'm pretty sure one can come up with a "reasonable " overload with
perfectly specified results, although I don't see the point.

--
Best regards,
Andrey Tarasevich

[Kira Yamato]

[OT]: x = 0; x += ++x + x++; x == 4?

On 2008-02-22 12:24:11 -0500, Johannes Bauer <dfnsonfsduifb@ gmx.desaid:

Pete Becker schrieb:
>

>A more important question, though, is "who cares?" Is it really
>worhwhile spending time talking about the hypothetical meaning of an
>expression that should never appear in real-world code? Even under
>Java's rules, where the result is well defined, the code is abominable.

>
Exactly, I fully second that. I do not understand at all why this exact
question comes up in this group (and in comp.lang.c, too, BTW) every few
days. Kind of annoying. You should think people have more important
problems.

It's called knowing your tools well. If you just don't know the
answer, then just say so or better yet just be quiet.

With a tool like C++ where you can write syntactically correct code but
with undefined behavior, it's good to know when you could be writing
such code or be reading such code from another programmer. And that is
exact what the OP asked: Is this code well-defined in C++?

Furthermore, the OP did not say this is production code. He did not
ask if this code is abominable or not. It is just an inquisition about
the rules of C++. So why shouldn't this question be raised in this
forum? Which forum should this post go where it won't be annoying?

--

// kira

[jason.cipriani@gmail.com]

Re: : x = 0; x += ++x + x++; x == 4?

On Feb 22, 5:12 pm, Kira Yamato <kira...@earthl ink.netwrote:

On 2008-02-22 12:24:11 -0500, Johannes Bauer <dfnsonfsdu...@ gmx.desaid:

Pete Becker schrieb:

A more important question, though, is "who cares?" Is it really
worhwhile spending time talking about the hypothetical meaning of an
expression that should never appear in real-world code? Even under
Java's rules, where the result is well defined, the code is abominable.

>

Exactly, I fully second that. I do not understand at all why this exact
question comes up in this group (and in comp.lang.c, too, BTW) every few
days. Kind of annoying. You should think people have more important
problems.

>
It's called knowing your tools well. If you just don't know the
answer, then just say so or better yet just be quiet.

Exactly. And not only that, but these kinds of questions (aside from
being just plain interesting to some people, like me) can stem from
perfectly reasonable, real-world situations. Perhaps you come across a
bug in your code and narrow it down to some weird C++ problem; you
construct a minimal example just as you are supposed to, and you come
here and ask about it without giving background context. That's
another good reason for posting those kinds of questions here. It's
*exactly* the kind of topic that this newsgroup exists for.

[Pete Becker]

Re: [OT]: x = 0; x += ++x + x++; x == 4?

On 2008-02-22 17:12:35 -0500, Kira Yamato <kirakun@earthl ink.netsaid:

On 2008-02-22 12:24:11 -0500, Johannes Bauer <dfnsonfsduifb@ gmx.desaid:
>

>Pete Becker schrieb:
>>

>>A more important question, though, is "who cares?" Is it really
>>worhwhile spending time talking about the hypothetical meaning of an
>>expression that should never appear in real-world code? Even under
>>Java's rules, where the result is well defined, the code is abominable.

>>
>Exactly, I fully second that. I do not understand at all why this exact
>question comes up in this group (and in comp.lang.c, too, BTW) every few
>days. Kind of annoying. You should think people have more important
>problems.

>
It's called knowing your tools well. If you just don't know the
answer, then just say so or better yet just be quiet.
>

If an apprentice carpenter asks whether he can use a hammer to drive in
a screw, he should be told "No." Speculating on whether it might or
might not work in some cases doesn't help him learn how to do his job.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

[jason.cipriani@gmail.com]

Re: : x = 0; x += ++x + x++; x == 4?

On Feb 22, 7:07 pm, Pete Becker <p...@versatile coding.comwrote :

If an apprentice carpenter asks whether he can use a hammer to drive in
a screw, he should be told "No." Speculating on whether it might or
might not work in some cases doesn't help him learn how to do his job.

I completely agree. The carpenter should answer his question. The
friendly carpenter may even want to have a discussion about it. The
carpenter should *not* say "who cares?". And in any case, both
apprentice and carpenter would raise an eyebrow at and then disregard
the comment of a third guy who walked in the room out of nowhere and
said "why are you two talking about this?".

Unless you meant something else by your metaphor?

[Kira Yamato]

Re: [OT]: x = 0; x += ++x + x++; x == 4?

On 2008-02-22 19:07:12 -0500, Pete Becker <pete@versatile coding.comsaid:

On 2008-02-22 17:12:35 -0500, Kira Yamato <kirakun@earthl ink.netsaid:
>

>On 2008-02-22 12:24:11 -0500, Johannes Bauer <dfnsonfsduifb@ gmx.desaid:
>>

>>Pete Becker schrieb:
>>>
>>>A more important question, though, is "who cares?" Is it really
>>>worhwhile spending time talking about the hypothetical meaning of an
>>>expression that should never appear in real-world code? Even under
>>>Java's rules, where the result is well defined, the code is abominable.
>>>
>>Exactly, I fully second that. I do not understand at all why this exact
>>question comes up in this group (and in comp.lang.c, too, BTW) every few
>>days. Kind of annoying. You should think people have more important
>>problems.

>>
>It's called knowing your tools well. If you just don't know the
>answer, then just say so or better yet just be quiet.
>>

>
If an apprentice carpenter asks whether he can use a hammer to drive in
a screw, he should be told "No." Speculating on whether it might or
might not work in some cases doesn't help him learn how to do his job.

Are you kidding me? It is in the speculation of various scenarios that
we explore and learn the limits and strengths of our tools.

--

// kira

[jason.cipriani@gmail.com]

Re: : x = 0; x += ++x + x++; x == 4?

On Feb 22, 7:59 pm, Kira Yamato <kira...@earthl ink.netwrote:

Are you kidding me? It is in the speculation of various scenarios that
we explore and learn the limits and strengths of our tools.

No, Pete is absolutely correct. There's no point in learning more
about your tools, or having interesting discussions about them. You
should just use them without question and get the job done without
thinking. Just don't hire "Versatile Coding" to do anything for you if
you need anything more than a typing grunt.

[jason.cipriani@gmail.com]

Re: : x = 0; x += ++x + x++; x == 4?

On Feb 22, 8:07 pm, "jason.cipri... @gmail.com"
<jason.cipri... @gmail.comwrote :

No, Pete is absolutely correct. There's no point in learning more
about your tools, or having interesting discussions about them. You
should just use them without question and get the job done without
thinking. Just don't hire "Versatile Coding" to do anything for you if
you need anything more than a typing grunt.

Apologies, Pete. That was uncalled for -- I meant "Roundhouse
Consulting".

[Pete Becker]

Re: : x = 0; x += ++x + x++; x == 4?

On 2008-02-22 19:13:39 -0500, "jason.cipriani @gmail.com"
<jason.cipriani @gmail.comsaid:

On Feb 22, 7:07 pm, Pete Becker <p...@versatile coding.comwrote :

>If an apprentice carpenter asks whether he can use a hammer to drive in
>a screw, he should be told "No." Speculating on whether it might or
>might not work in some cases doesn't help him learn how to do his job.

>
I completely agree. The carpenter should answer his question. The
friendly carpenter may even want to have a discussion about it.

Interesting. You "completely agree" with something I clearly didn't say.

The
carpenter should *not* say "who cares?". And in any case, both
apprentice and carpenter would raise an eyebrow at and then disregard
the comment of a third guy who walked in the room out of nowhere and
said "why are you two talking about this?".
>
Unless you meant something else by your metaphor?

I meant just what I said. "No" is all that needs to be said, although
in a suitable setting it can be accompanied by laughter.

Unreadable code is unreadable code, regardless of whether its effect is
well defined.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)