a question

[c/c++ programming lover]

Could anyone tell me why the result is that:
printf("%d",++5 *++5);
the result is 49?
thanks

[Juha Nieminen]

Re: a question

c/c++ programming lover wrote:

Could anyone tell me why the result is that:
printf("%d",++5 *++5);
the result is 49?

error: lvalue required as increment operand

[blargg]

Re: a question

Juha Nieminen wrote:

c/c++ programming lover wrote:

Could anyone tell me why the result is that:
printf("%d",++5 *++5);
the result is 49?

>
error: lvalue required as increment operand

Maybe 49 is the error code his compiler gives for such an error.

[Victor Bazarov]

Re: a question

blargg wrote:

Juha Nieminen wrote:

>c/c++ programming lover wrote:

>>Could anyone tell me why the result is that:
>>printf("%d",+ +5*++5);
>>the result is 49?

>error: lvalue required as increment operand

>
Maybe 49 is the error code his compiler gives for such an error.

I think 'lover' just was asking about

int a = 5;
printf("%d", ++a*++a); // prints 49

Which has undefined behaviour last time I looked.

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

[Salt_Peter]

Re: a question

On Nov 7, 4:20 am, "c/c++ programming lover" <564462...@qq.c omwrote:

Could anyone tell me why the result is that:
printf("%d",++5 *++5);
the result is 49?
thanks

It doesn't matter what the result is. Its undefined behavior.

[Juha Nieminen]

Re: a question

Salt_Peter wrote:

On Nov 7, 4:20 am, "c/c++ programming lover" <564462...@qq.c omwrote:

>Could anyone tell me why the result is that:
>printf("%d",++ 5*++5);
>the result is 49?
>thanks

>
It doesn't matter what the result is. Its undefined behavior.

Does the standard really specify a syntax error as "undefined behavior"?

[Salt_Peter]

Re: a question

On Nov 7, 5:49 pm, Juha Nieminen <nos...@thanks. invalidwrote:

Salt_Peter wrote:

On Nov 7, 4:20 am, "c/c++ programming lover" <564462...@qq.c omwrote:

Could anyone tell me why the result is that:
printf("%d",++5 *++5);
the result is 49?
thanks

>

It doesn't matter what the result is. Its undefined behavior.

>
Does the standard really specify a syntax error as "undefined behavior"?

Its a syntax error, yes, thats the obvious answer. Error or not, the
OP's intent was to ask what the following might have a guaranteed
result:

int n(5);
printf("%d",++n *++n);

[James Kanze]

Re: a question

On Nov 7, 11:49 pm, Juha Nieminen <nos...@thanks. invalidwrote:

Salt_Peter wrote:

On Nov 7, 4:20 am, "c/c++ programming lover" <564462...@qq.c omwrote:

Could anyone tell me why the result is that:
printf("%d",++5 *++5);
the result is 49?
thanks

It doesn't matter what the result is. Its undefined
behavior.

Does the standard really specify a syntax error as "undefined
behavior"?

It does, actually. The implementation is required to emit a
diagnostic, but what happens next is undefined behavior.

In practice, of course, from a QoI point of view, the
implementation will normally not generate an object file. The
rule is there to allow the implementation to use ill-formed
constructs as an extension; once the compiler has output a
diagnostic (the message "this is an extension", for example),
it's free to go on and compile the code, assigning any meaning
it wants to it.

--
James Kanze (GABI Software) email:james.kan ze@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientier ter Datenverarbeitu ng
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[anon]

Re: a question

Salt_Peter wrote:

On Nov 7, 5:49 pm, Juha Nieminen <nos...@thanks. invalidwrote:

>Salt_Peter wrote:

>>On Nov 7, 4:20 am, "c/c++ programming lover" <564462...@qq.c omwrote:
>>>Could anyone tell me why the result is that:
>>>printf("%d", ++5*++5);
>>>the result is 49?
>>>thanks
>>It doesn't matter what the result is. Its undefined behavior.

> Does the standard really specify a syntax error as "undefined behavior"?

>
Its a syntax error, yes, thats the obvious answer. Error or not, the
OP's intent was to ask what the following might have a guaranteed
result:
>
int n(5);
printf("%d",++n *++n);

Intent or not, what he wrote produces a syntax error.