A newbie question about STL under GCC

Hello,

I am learning STL using G++ under Ubuntu. Today I copied following C++ code from a text book (Absolute C++) and tried to run it:

Code:

#include <iostream>
#include <vector>
using std::cout;
using std::endl;
using std::vector;
using std::vector<int>::iterator;

int main()
{
vector<int> container;
for (int i=1;i<=4;i++)
container.push_back(i);

cout << "Here is what is in the container:\n";
iterator p;
for (p=container.begin();p!=container.end();p++)
cout << *p << " ";
cout << endl;
}

When I compile it, got following error:

STL_vector.cpp:6: error: ‘std::vector<int, std::allocator<int> >’ is not a namespace

So, what's the problem of: using std::vector<int>::iterator;

Sorry for this kind of newbie question. Thanks in advance for your help.

regards,
Derek
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Originally Posted by featips

Hello,

I am learning STL using G++ under Ubuntu. Today I copied following C++ code from a text book (Absolute C++) and tried to run it:

Code:

#include <iostream>
#include <vector>
using std::cout;
using std::endl;
using std::vector;
using std::vector<int>::iterator;

int main()
{
vector<int> container;
for (int i=1;i<=4;i++)
container.push_back(i);

cout << "Here is what is in the container:\n";
iterator p;
for (p=container.begin();p!=container.end();p++)
cout << *p << " ";
cout << endl;
}

When I compile it, got following error:

STL_vector.cpp:6: error: ‘std::vector<int, std::allocator<int> >’ is not a namespace

So, what's the problem of: using std::vector<int>::iterator;

Sorry for this kind of newbie question. Thanks in advance for your help.

regards,
Derek
Reply With Quote

"Quote"
[ubuntu] GCC question - Ubuntu Forums

lol cyberfish....

Anyway, iterator isn't a namespace that's why. Maybe it meant "typedef std::vector<int>::iterator iterator" not "using std::vector<int>::iterator"

Originally Posted by featips

Hello,

I am learning STL using G++ under Ubuntu. Today I copied following C++ code from a text book (Absolute C++) and tried to run it:

Code:

#include <iostream>
#include <vector>
using std::cout;
using std::endl;
using std::vector;
using std::vector<int>::iterator;

int main()
{
vector<int> container;
for (int i=1;i<=4;i++)
container.push_back(i);

cout << "Here is what is in the container:\n";
iterator p;
for (p=container.begin();p!=container.end();p++)
cout << *p << " ";
cout << endl;
}

When I compile it, got following error:

STL_vector.cpp:6: error: ‘std::vector<int, std::allocator<int> >’ is not a namespace

So, what's the problem of: using std::vector<int>::iterator;

Sorry for this kind of newbie question. Thanks in advance for your help.

regards,
Derek
Reply With Quote

The way that the 'using' syntax works, is that you can specify something without qualifying what *namespace* it exists in. The namespace can be nested within another namespace, such as foo::bar::baz. So basically:

using namespace NAMESPACE;
using NAMESPACE::class;
using NAMESPACE::object;

Code:

using std::cout;
using std::endl;
using std::vector;

int main()
{
    typedef vector<int> container_t;
    typedef container_t::iterator iterator_t;
    container_t container;
    for (int i=1;i<=4;i++)
        container.push_back(i);
    cout << "Here is what is in the container:\n";
    iterator_t p;
    for (p=container.begin();p!=container.end();p++)
        cout << *p << " ";
    cout << endl;
    return 0;
}