Using Templates in C++
-Sanchit Karve
born2c0de@hotmail.com
Now let us assume that we have a Stack class(Data Structure) that is capable
of storing only int's. Now suppose you want it to store float's as well. You
would normally write the whole class again by copy/pasting the previous class
and make the necessary changes. But hey,There is a much better alternative. Using
templates, you can manage just one class that handles different data-types. That
way even if you find an error in your class, fixing it will make changes to all
the data-types. Here is an example of a templated stack data structure.
#include <iostream.h> // For I/0
#include <windows.h> // FOR MessageBox() API
#include <conio.h>
#define MAX 10 // MAXIMUM STACK CONTENT
template <class T> // Using Templates so that any type of data can be
// stored in Stack without multiple defination of class
class stack
{
protected:
T arr[MAX]; // Contains all the Data
public:
T item,r;
int top; //Contains location of Topmost Data pushed onto Stack
stack() //Constructor
{
for(int i=0;i<MAX;i++)
{
arr[i]=NULL; //Initialises all Stack Contents to NULL
}
top=-1; //Sets the Top Location to -1 indicating an empty stack
}
void push(T a) // Push ie. Add Value Function
{
top++; // increment to by 1
if(top<MAX)
{
arr[top]=a; //If Stack is Vacant store Value in Array
}
else // Bug the User
{
MessageBox(0,"STACK IS FULL","STACK WARNING!",MB_ICONSTOP);
top--;
}
}
T pop() // Delete Item. Returns the deleted item
{
if(top==-1)
{
MessageBox(0,"STACK IS EMPTY\n","WARNING",MB_ICONSTOP);
return NULL;
}
else
{
T data=arr[top]; //Set Topmost Value in data
arr[top]=NULL; //Set Original Location to NULL
top--; // Decrement top by 1
return data; // Return deleted item
}
}
};
void main()
{
stack <int>a; // Create object of class a with int Template
int opt=1;
while (opt!=3)
{
clrscr();
cout<<" MAX STACK CAPACITY="<<((MAX-a.top)-1)<<"\n\n\n\n";
cout<<"1) Push Item\n";
cout<<"2) Pop Item\n";
cout<<"3) Exit\n\n";
cout<<"Option?";
cin>>opt;
switch(opt)
{
case 1:
cout<<"Which Number should be pushed?";
cin>>a.item;
a.push(a.item);
break;
case 2:
a.r=a.pop();
cout<<"Item popped from Stack is:"<<a.r<<endl;
sleep(2);
break;
}
}
}
Everything looks similiar except an object declaration:
This means that the value T is substituted by int. User-Defined Data Types
can also be used provided the required overloaded operator functions are
present.
In case if we define the class functions outside the templated class, the
syntax changes a bit. For a Constructor:
stack <T>::stack()
{
//div
}
Yes, we have to define that template thing everytime we write a function
outside the class.But if a function returns an object of the same
templated class the syntax would be like this:
{
//div
}
Templates can also have pre-defined values like this:
class stack
{
private:
T data[max];
//rest of the members...
};
Templates can be inherited as well like this:
{
//members...
};
That's all about templates. If you use Templates frequently you will save
a lot of typing and debugging time.
Suggestions\Questions can be brought to my notice atborn2c0de@hotmail.com
HAVE FUN CODING!!!
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