variable declaration

[widmont]

Hello,

I would like to know the difference between two variable declaration
ways:

int point(0);

and

int point=0;

Thanks for your help!!

A.

[Tomás]

Re: variable declaration

widmont posted:
[color=blue]
> Hello,
>
> I would like to know the difference between two variable declaration
> ways:
>
> int point(0);
>
> and
>
> int point=0;
>
> Thanks for your help!!
>
> A.[/color]

When you're working with intrinsic types, there's no difference whatsoever.
It's a situation of "Thanks" Vs. "Thank you". Pick whichever tickles your
fancy.

Be careful though. If you want to "default initialise" something, then you
can't simply write:

int point();

That my friend is a function declaration. You can work your way around this
with:

int point = int();

But unfortunately, the type you're working with must have a public copy
constructor. So it won't work with "ostringstream" :

ostringstream blah = ostringstream() ;


Fortunately though, if your type is a POD, you can do this:

PodType object = {};

(I'm open to correction on whether the above actually zero initializes
everything. If memory serves me right, then it does.)

When you have a contructor which takes more than one argument, then you
*have* to use the parenthesis form, eg.:

Dog benji("Benji",7 );

You can't do:

Dog benji = "Benji", 7;


If you want to know how to default initialise something that has a non-
public copy constructor, then:

template<class T>
class DefaultInitiali sed : public T
{

DefaultInitiali sed() : T()
};

int main()
{
DefaultInitiali sed<ostringstre am> k;
}


-Tomás

[Tomás]

Re: variable declaration

[color=blue]
> template<class T>
> class DefaultInitiali sed : public T
> {
>
> DefaultInitiali sed() : T()[/color]

{

}
[color=blue]
> };
>
> int main()
> {
> DefaultInitiali sed<ostringstre am> k;
> }[/color]

[Victor Bazarov]

Re: variable declaration

widmont wrote:[color=blue]
> I would like to know the difference between two variable declaration
> ways:
>
> int point(0);
>
> and
>
> int point=0;[/color]

In this particular case (with 'int'), none.

V
--
Please remove capital As from my address when replying by mail

[Rolf Magnus]

Re: variable declaration

Tomás wrote:
[color=blue]
> widmont posted:
>[color=green]
>> Hello,
>>
>> I would like to know the difference between two variable declaration
>> ways:
>>
>> int point(0);
>>
>> and
>>
>> int point=0;
>>
>> Thanks for your help!!
>>
>> A.[/color]
>
> When you're working with intrinsic types, there's no difference
> whatsoever. It's a situation of "Thanks" Vs. "Thank you". Pick whichever
> tickles your fancy.
>
> Be careful though. If you want to "default initialise" something, then you
> can't simply write:
>
> int point();
>
> That my friend is a function declaration. You can work your way around
> this with:
>
> int point = int();
>
> But unfortunately, the type you're working with must have a public copy
> constructor. So it won't work with "ostringstream" :
>
> ostringstream blah = ostringstream() ;[/color]

No, but you can simply do:

ostringstream blah;

This will give you a default initialized variable, if the type is non-POD.
[color=blue]
> Fortunately though, if your type is a POD, you can do this:
>
> PodType object = {};[/color]

I think this only works for compound types.
[color=blue]
> (I'm open to correction on whether the above actually zero initializes
> everything. If memory serves me right, then it does.)[/color]

It default-initializes everything, which means zero for integer types.
[color=blue]
> When you have a contructor which takes more than one argument, then you
> *have* to use the parenthesis form, eg.:
>
> Dog benji("Benji",7 );
>
> You can't do:
>
> Dog benji = "Benji", 7;
>
>
> If you want to know how to default initialise something that has a non-
> public copy constructor, then:
>
> template<class T>
> class DefaultInitiali sed : public T
> {
>
> DefaultInitiali sed() : T()
> };[/color]

That constructor is private.
[color=blue]
> int main()
> {
> DefaultInitiali sed<ostringstre am> k;
> }[/color]

[Marcus Kwok]

Re: variable declaration

"Tom?s" <NULL@null.null > wrote:[color=blue]
> When you have a contructor which takes more than one argument, then you
> *have* to use the parenthesis form, eg.:
>
> Dog benji("Benji",7 );
>
> You can't do:
>
> Dog benji = "Benji", 7;[/color]

However, you can do:

Dog benji = Dog("Benji", 7);

(assuming the appropriate copy-constructors, etc., are accessible).

--
Marcus Kwok