initialization of a struct in a vector

[Jayw710]

hi all,

this should be basic, but I can't seem to get the right syntax.

i have a struct

struct PTStruct
{
int x;
int y;
};

class abc
{
public:
abc();
...

std::vector<PTS truct> mypoints;
}

void abc::abc() : mypoints(100)
{

}
and i'm trying to get all the PTStruct variables (x and y) in mypoints to be
initialized to zero, but I'm screwing up the syntax somehow.

Any suggestions how this should be done?

Thanks to all!

Jay

[Andrey Tarasevich]

Real Name wrote:

And 'PTStruct()' is an instance of
'PTStruct' with both fields set to 0.

Why? PTStruct only contains PODs - their default ctors wont we called
implicit, you have to call them explicit in your own ctor.
...

'PTStruct' is a POD type. Initializer '()' for a POD type causes default
initialization being applied to all its members. Default initialization
for type 'int' is zero initialization. That's all.

BTW, it has nothing to do with any "constructo rs". Default
initialization process for POD types does not involve constructors.
Moreover, objects of type 'int' have no constructors at all, default or
not.

--
Best regards,
Andrey Tarasevich

[Real Name]

"Andrey Tarasevich" <an************ **@hotmail.com> schrieb im Newsbeitrag
news:11******** *****@news.supe rnews.com...

Real Name wrote:

And 'PTStruct()' is an instance of
'PTStruct' with both fields set to 0.
Why? PTStruct only contains PODs - their default ctors wont we called
implicit, you have to call them explicit in your own ctor.
...

'PTStruct' is a POD type.

Its a struct/class of PODs - it not a POD itself.
Initializer '()' for a POD type causes default
initialization being applied to all its members. Default initialization
for type 'int' is zero initialization. That's all.
Ack. But has nothing to do with PTStruct(): the members wont be initialized.
If you have any other information please point me to the relevant part of
the standard.
BTW, it has nothing to do with any "constructo rs". Default
initialization process for POD types does not involve constructors.
Call it as you want.
Moreover, objects of type 'int' have no constructors at all, default or
not.

So you think we are unable to construct an integer?

regards,
me

[Andrey Tarasevich]

Real Name wrote:

>> And 'PTStruct()' is an instance of
>> 'PTStruct' with both fields set to 0.
>
> Why? PTStruct only contains PODs - their default ctors wont we called
> implicit, you have to call them explicit in your own ctor.
> ...
'PTStruct' is a POD type.

Its a struct/class of PODs - it not a POD itself.

Huh? It _is_ a POD itself. You probably need to look up a definition of
POD type. See 3.9/10 in the standard.

Initializer '()' for a POD type causes default
initialization being applied to all its members. Default initialization
for type 'int' is zero initialization. That's all.

Ack. But has nothing to do with PTStruct(): the members wont be initialized.

Not true. See below.
If you have any other information please point me to the relevant part of
the standard.

See 8.5/7:

--
8.5/7
An object whose initializer is an empty set of parentheses, i.e. (),
shall be default-initialized.
--

Then 8.5/5 to find out what "default-initialized" means in this case of
POD-type:

--
8.5/5
[...]
- otherwise, the storage for the object is zero-initialized
--

BTW, it has nothing to do with any "constructo rs". Default
initialization process for POD types does not involve constructors.

Call it as you want.

That's, BTW, is an important detail, not just a matter of "calling it as
someone wants".

Moreover, objects of type 'int' have no constructors at all, default or
not.

So you think we are unable to construct an integer?
...

"Construct" ? No. You are unable to construct an integer. Only objects of
class types can be constructed. In the standard C++ terminology the
notion of "constructi on" is not applicable to non-class types.
Apparently, you are mixing the concept of "constructi on" with more
general concept of "initialization ". These are not the same in C++.

--
Best regards,
Andrey Tarasevich

[Real Name]

"Andrey Tarasevich" <an************ **@hotmail.com> schrieb im Newsbeitrag
news:11******** *****@news.supe rnews.com...

Huh? It _is_ a POD itself. You probably need to look up a definition of
POD type. See 3.9/10 in the standard.
Thx - that helped a lot.

Ack. But has nothing to do with PTStruct(): the members wont be initialized.
Not true. See below.

I have not seen any compiler doing so...
If you have any other information please point me to the relevant part of the standard.

See 8.5/7:

Thx again.