Global namespace pollution

[Birt]

An article states: the global namespace be polluted, causing "a namespace
collision."

What does this mean exactly? Thank you very much!

[John Harrison]

"Birt" <bi***@imp.com> wrote in message
news:r5******************@bgtnsc05-news.ops.worldnet.att.net...

An article states: the global namespace be polluted, causing "a namespace
collision."

What does this mean exactly? Thank you very much!

This is OK.

namespace X
{
int g;
}
int g;
int main()
{
g = 0; // no problem
}
This is not.

namespace X
{
int g;
}
int g;
using namespace X; // pollution

int main()
{
g = 0; // which g?
}

In C++ I think the dangers of pollution are overstated, a bit like the real
world.

john

[Sharad Kala]

"Birt" <bi***@imp.com> wrote in message
news:r5******************@bgtnsc05-news.ops.worldnet.att.net...

An article states: the global namespace be polluted, causing "a namespace
collision."

What does this mean exactly? Thank you very much!

When you write using namespace X, the names in that namespace are made visible
in the current scope.

Say,
namespace X{
class Y{
};
}
class Y{
};
int main(){
Y y; // OK
}

Next write using namespace X, so class Y gets introduced in the current scope.

namespace X{
class Y{
};
}
using namespace X;
class Y
{
};
int main{
Y y; // Error...Y is ambiguous
}

-Sharad