TEMPLATES IN C++

Templates are the foundation of generic programming which involves writing code in a way that is independent of any particular type.

Hello Friends Today I am going to learn about Template in C++. That how to use Template inn C++. A template is a blueprint or formula for creating a generic class or a function. The library containers like iterators, and algorithms are examples of generic programming and have been developed using template concept.
There is a single definition of each container, such as vector, but we can define many different kinds of vectors for example, vector or vector .
You can use templates to define functions as well as classes, let us see how do they work:
Function Template: The general form of a template function definition is shown here:
template ret-type func-name(parameter list)
{
// body of function
}
Here, type is a placeholder name for a data type used by the function. This name can be used within the function definition.
The following is the example of a function template that returns the maximum of two values:
#include
#include
using namespace std;
template
inline T const& Max (T const& a, T const& b)
{
return a < b ? b:a;
}
int main ()
{
int i = 39;
int j = 20;
cout << "Max(i, j): " << Max(i, j) << endl;
double f1 = 13.5;
double f2 = 20.7;
cout << "Max(f1, f2): " << Max(f1, f2) << endl;
string s1 = "Hello";
string s2 = "World";
cout << "Max(s1, s2): " << Max(s1, s2) << endl;
return 0;
}

If we compile and run above code, this would produce following result:
Max(i, j): 39
Max(f1, f2): 20.7
Max(s1, s2): World

Class Template:
Just as we can define function templates, we can also define class templates. The general form of a generic class declaration is shown here:
template class class-name {
.
.
.
}
Here, type is the placeholder type name, which will be specified when a class is instantiated. You can define more than one generic data type by using a comma-separated list.
Following is the example to define class Stack<> and implement generic methods to push and pop the elements from the stack:
#include
#include
#include
#include
#include
using namespace std;
template
class Stack {
private:
vector elems; // elements
public:
void push(T const&); // push element
void pop(); // pop element
T top() const; // return top element
bool empty() const{ // return true if empty.
return elems.empty();
}
};
template
void Stack::push (T const& elem)
{
// append copy of passed element
elems.push_back(elem);
}
template
void Stack::pop ()
{
if (elems.empty()) {
throw out_of_range("Stack<>::pop(): empty stack");
}
// remove last element
elems.pop_back();
}
template
T Stack::top () const
{
if (elems.empty()) {
throw out_of_range("Stack<>::top(): empty stack");
}
// return copy of last element
return elems.back();
}
int main()
{
try {
Stack intStack; // stack of ints
Stack stringStack; // stack of strings
// manipulate int stack
intStack.push(7);
cout << intStack.top() < // manipulate string stack
stringStack.push("hello");
cout << stringStack.top() << std::endl;
stringStack.pop();
stringStack.pop();
}
catch (exception const& ex) {
cerr << "Exception: " << ex.what() < return -1;
}
}
If we compile and run above code, this would produce following result:
7
hello
Exception: Stack<>::pop(): empty stack
I think this post will help you.I think this post will help you.
Thanks!!!
If any query about this post then put your comment in comment box below..

Posted in: Advance C