Confused about what a template dose

[LEARNING2slowly]

I completely don't understand any thing about templates. I read books on C++ to help but i just don't get what are they for and how to use them i thought they were for classes to have one class but for many types but am still not certain.
Can some one help me understand how to use them and what they are for.



sorry for my bad spelling etc. :)

[coder777]

template paramter are a kind of placeholders for types and constants.

whithin the template class/function you can use variables of [unknown] type the way you want it.

In order to use a templated class/function you must provide a real type (which supports operations done with the template parameter).

templates are usually used in libraries like STL.

[LEARNING2slowly]

Thanks

[nkendra]

Templates enable code reuse, by allowing a function or class to work with different types.

// A function example:

// Swap value1 with value2
template <class T> 
void swap ( T& value1, T& value2)
{
    T temp = value1;
    value1 = value2;
    value1 = temp;
}

// ... many lines later in another function
int v1 = 5;
int v2 = 20;
swap(v1, v2); // now v2 = 5 and v1 = 20
// strings and other types can be swapped too

Containers are often implemented as templates to allow them to work with multiple types.

int main(void)
{
    // a vector is basically an array
    vector<int> intVector;
    intVector.push_back(1); // add the number 1 to the array
    intVector.push_back(2); // add 2 to the array
    cout << intVector[0] << " " << intVector[1] << endl; // prints: 1 2

    // a vector of strings
    vector<string> strVector;
    strVector.push_back("hello");
    strVector.push_back("world!");
    cout << strVector[0] << " " << strVector[1] << endl; // prints: hello world!
    return 0;
}

Disclaimer: This code will not work if it's just copy-pasted; additional libraries must be included. I did not compile this code so there my be syntax or other errors.