A template is a simple and yet very powerful tool in C++. The simple idea is to pass data type as a parameter so that we don't need to write the same code for different data types. For example, a software company may need sort() for different data types.
A template is a simple and yet very powerful tool in C++. The simple idea is to pass data type as a parameter so that we don’t need to write the same code for different data types. For example, a software company may need sort() for different data types. Rather than writing and maintaining the multiple codes, we can write one sort() and pass data type as a parameter.
C++ adds two new keywords to support templates: ‘template’ and ‘typename’. The second keyword can always be replaced by keyword ‘class’.
Templates are expanded at compiler time. This is like macros. The difference is, compiler does type checking before template expansion. The idea is simple, source code contains only function/class, but compiled code may contain multiple copies of same function/class.
We write a generic function that can be used for different data types. Examples of function templates are sort(), max(), min(), printArray().
Following is a simple example of template Array class.
#include <iostream>
using namespace std;
template <typename T>
class Array {
private:
T *ptr;
int size;
public:
Array(T arr[], int s);
void print();
};
template <typename T>
Array<T>::Array(T arr[], int s) {
ptr = new T[s];
size = s;
for(int i = 0; i < size; i++)
ptr[i] = arr[i];
}
template <typename T>
void Array<T>::print() {
for (int i = 0; i < size; i++)
cout<<" "<<*(ptr + i);
cout<<endl;
}
int main() {
int arr[5] = {1, 2, 3, 4, 5};
Array<int> a(arr, 5);
a.print();
return 0;
}
Output:
1 2 3 4 5
