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
Reply With Quote

Quote:

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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"

Quote:

---

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;
}

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