C / C++ / MFC

Re: array of zero elements

17-Feb-08 23:03

Thanks kakan,

I mean I am reading code by others. Smile | :)

regards,
George

Hamid_RT18-Feb-08 7:31

18-Feb-08 7:31

Not exactly we. Poke tongue | ;-P

int const&

George_George16-Feb-08 23:17

Re: int const& [modified]

16-Feb-08 23:17

Hello everyone,

We always write const int other than int const, are they the same?

Example,

int const & x = 10;

const int& y = 10;

thanks in advance,
George

Rajkumar R17-Feb-08 2:01

Rajkumar R

17-Feb-08 2:01

type qualifiers are used to modify the property of type of the identifier.

so,

"int const x" and "const int x" are same, as const qualifier modifies the type "int" of identifier x.

the change of qualifier position has effect say,
"int const *x" and "int *const x" this is different, as const qualifier modifies the type "int" of expression (*x) for former and const qualifier modifies the type "int *" of identifier "x" for later.

and "int const *x" and "const int *x" are same, as both const qualifier modifies the type "int" of expression (*x)

similarly "int const &x" and "const int &y" are same and "int const &x" and "int & const x" are different although the later is ignored.

modified on Sunday, February 17, 2008 10:24 PM

George_George17-Feb-08 2:05

17-Feb-08 2:05

Thanks Rajkumar,

Rajkumar R wrote:
"int const &x" and "int & const x" are different although the former is not allowed.

Why the former "int const &x" is not allowed? The following code can compile in Visual Studio 2008. Smile | :)

int main()
{
	int const &x = 10;

	return 0;
}

regards,
George

Rajkumar R17-Feb-08 2:11

Rajkumar R

17-Feb-08 2:11

sorry typo error i mean "later", fixed.

George_George17-Feb-08 13:34

17-Feb-08 13:34

No Rajkumar,

it is allowed, but always ignored, since reference are always const.

Here is the code and related warning message,

main.cpp(4) : warning C4227: anachronism used : qualifiers on reference are ignored

int main()
{
	int i = 100;
	int & const x = i;

	return 0;
}

regards,
George

Rajkumar R17-Feb-08 16:23

Rajkumar R

17-Feb-08 16:23

"qualifiers on reference are ignored" means no effect on "const" qualifier
i.e; int &const x is taken as int &x;

i used to consider warning as error. (there is an option too (/WX) Smile | :)

)
if it is allowed it should not be ignored. Smile | :)

any way i can change my mind, "not allowed" to "ignored"

George_George17-Feb-08 16:25

17-Feb-08 16:25

Thanks Rajkumar,

My question is answered.

regards,
George

Priyanka sabharwal7-Aug-08 20:58

Priyanka sabharwal

7-Aug-08 20:58

Hi george,
Why had ref been implimented in this way that its a 'const' implictly. Why can not a reference when once bound to an object at time of declaration be allowed to bound to some other object? why this kind of restriction?

Regards
Priyanka

George_George9-Aug-08 1:29

9-Aug-08 1:29

Please try the following sample code,

int main()
{
	int a = 10;
	int b = 20;
	// if using const int& p, will not compile
	int& pi = a;
	pi = b;
	
	return 0;
}

regards,
George

Hamid_RT18-Feb-08 7:27

18-Feb-08 7:27

See this[^] thread if helpfuls for you.

George_George18-Feb-08 19:47

18-Feb-08 19:47

Thanks Hamid,

I have read the link, but I do not think it relates to my question. The discussion is about const reference to temporary object, but I am talking about whether int const& or const int& is better. Smile | :)

regards,
George

Hamid_RT18-Feb-08 20:08

18-Feb-08 20:08

No it was for const& not your question I think its helpful for you,ok? Wink | ;)

George_George18-Feb-08 20:12

18-Feb-08 20:12

Sure, helpful. Thanks Hamid!

regards,
George

Hamid_RT18-Feb-08 20:44

18-Feb-08 20:44

You're welcome.

George_George18-Feb-08 20:54

18-Feb-08 20:54

Thanks for your continuous help, Hamid!

Hope we can always have other topics to discuss in the future. Smile | :)

regards,
George

Hamid_RT18-Feb-08 21:18