Templates Confusion

Guys I have this simple code on templates

Code:

---

#include <iostream.h>
#include <vector>
 
template <typename T>
class MyQueue
{
    std::vector<T> data;
public:
    void Add(T const &);
    void Remove();
    void Print();
};
 
template <typename T> void MyQueue<T> ::Add(T const &d)
{
    data.push_back(d);
}
 
template <typename T> void MyQueue<T>::Remove()
{
    data.erase(data.begin( ) + 0,data.begin( ) + 1);
}
 
template <typename T> void MyQueue<T>::Print()
{
    std::vector <double>::iterator It1;
    It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout << " " << *It1<<endl;
 
}
 
 
int main (int argc,char *argv[])
{
    MyQueue<double> q;
    q.Add(1.34);
    q.Add(2.24);
 
    cout<<"Before removing data"<<endl;
    q.Print();
 
    q.Remove();
    cout<<"After removing data"<<endl;
    q.Print();
    return 0;
}

---

in my

Quote:

---

template <typename T> void MyQueue<T>::Print()

---

method I want this iterator to be synchronize with my typename T

Code:

---

std::vector <double>::iterator It1;

---

meaning if i say

Code:

---

MyQueue<int> q;

---

the iterator should adjust himself to int, right now its always expecting a double.
Please help,
baray98

Wouldn't it be right to have std::vector <T>::iterator It1; ? Or am i missing something?

I think you are missing something. The way that i can think of specialized template where if
T (in my case) is not double , then do something like this on the print method

Code:

---

template <typename T> void MyQueue <T>::Print()
{
    std::vector <double>::iterator It1;
    It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout << " " << *It1<<endl;
}
template <> void MyQueue<long>::Print()
{
    std::vector <long>::iterator It1;
    It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout << " " << *It1<<endl;
 
 
}
template <> void MyQueue<int>::Print()
{
    std::vector <int>::iterator It1;
    It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout << " " << *It1<<endl;
}
template <> void MyQueue<bool>::Print()
{
    std::vector <bool>::iterator It1;
    It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout <<std::boolalpha << *It1<<endl;
}

---

but now I want to extract the real printing itself and have just one method that will do this

Code:

---

// this is the real printing part 
It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout <<std::boolalpha << *It1<<endl;

---

how can i have just one method to do all this on all type of T

baray98

What exactly is the problem? Is there an error message you could show us?

My problem is that in my class template method

Code:

---

template <typename T> void MyQueue<T>::Print(){
    std::vector <double>::iterator It1;
    It1 = data.begin();
    for ( It1 = data.begin( ) ; It1 != data.end( ) ; It1++ )
        cout << " " << *It1<<endl;
 }

---

this will only work for doubles since It1 is instantiated with doubles. I wanted to change this so that it will work on any T.

and the only thing i can think of is using special template and give each type a print method

baray98

replace

Code:

---

std::vector <double>::iterator It1;

---

by

Code:

---

typename std::vector<T>::iterator It1;
// Or make it a const_iterator since you do not want to modify things.
// For the same reason your method could (should) be declared const.

---

(You might want to provide a typedef for that in your class.)

HTH

If you want something to adjust "on the fly" then you can't do it with templates. What you want can probably be done with subclassing and virtual methods.