simple namespace question

[michael]

Hi all,

why if I can use

std::vector<int>::iterator variable;

can I not use

using std::vector<int>::iterator;

to save typing the std::vector<int>:: each time I use it?
I have a text which has the 'using' statement in it, but when I compile I
get errors like "std::vector<int, std::allocator<int>is not a namespace".
I don't understand why, if someone could explain it I would be gratefull.

Thanks for your help

Regards

Michael

[Gianni Mariani]

michael wrote:

Hi all,

why if I can use

std::vector<int>::iterator variable;

can I not use

using std::vector<int>::iterator;

That's illegal. This is legal.

typedef std::vector<int>::iterator iterator;

[Ian Collins]

michael wrote:

Hi all,

why if I can use

std::vector<int>::iterator variable;

can I not use

using std::vector<int>::iterator;

to save typing the std::vector<int>:: each time I use it?
I have a text which has the 'using' statement in it, but when I compile I
get errors like "std::vector<int, std::allocator<int>is not a namespace".
I don't understand why, if someone could explain it I would be gratefull.

The error says it all. You can only use a using directive with a
namespace. Use a typedef instead.

--
Ian Collins.

[michael]

"Ian Collins" <ia******@hotmail.comwrote in message
news:58**************@mid.individual.net...

michael wrote:

>Hi all,

why if I can use

std::vector<int>::iterator variable;

can I not use

using std::vector<int>::iterator;

to save typing the std::vector<int>:: each time I use it?
I have a text which has the 'using' statement in it, but when I compile I
get errors like "std::vector<int, std::allocator<int>is not a
namespace".
I don't understand why, if someone could explain it I would be gratefull.

The error says it all. You can only use a using directive with a
namespace. Use a typedef instead.

--
Ian Collins.

Thanks for the help Ian,

I'm still a bit confused though. What exactly makes
std::vector<int>::iterator not a namespace when for example std::endl is?
What is it that determines whether something is a namespace or not?

thanks for the help

regards

Michael

[Ian Collins]

michael wrote:

"Ian Collins" <ia******@hotmail.comwrote in message
news:58**************@mid.individual.net...

>>michael wrote:

>>>Hi all,

why if I can use

std::vector<int>::iterator variable;

can I not use

using std::vector<int>::iterator;

to save typing the std::vector<int>:: each time I use it?
I have a text which has the 'using' statement in it, but when I compile I
get errors like "std::vector<int, std::allocator<int>is not a
namespace".
I don't understand why, if someone could explain it I would be gratefull.

The error says it all. You can only use a using directive with a
namespace. Use a typedef instead.

*Please* don't quote signatures.

>
Thanks for the help Ian,

I'm still a bit confused though. What exactly makes
std::vector<int>::iterator not a namespace when for example std::endl is?
What is it that determines whether something is a namespace or not?

Using std::vector or using std::cout are legal. Using only works with a
namespace, or an object or value from a namespace, not a type from a
class in a namespace. std::vector<int>::iterator goes one step too far.
Use a typedef.

--
Ian Collins.