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is_pointer Template in C++

  • Last Updated : 19 Nov, 2018
Geek Week

The std::is_pointer template of C++ STL is used to check whether the given type is pointer or not. It returns a boolean value showing the same.

Syntax:

template <class T > struct is_pointer;

Parameter: This template accepts a single parameter T (Trait class) to check whether T is a pointer or not.

Return Value: This template returns a boolean value as shown below:

  • True: if the type is a pointer.
  • False: if the type is a non-pointer.

Below programs illustrate the std::is_pointer template in C++ STL:



Program 1:




// C++ program to illustrate
// is_pointer template
  
#include <iostream>
#include <type_traits>
using namespace std;
  
// main program
class GFG {
};
  
int main()
{
    cout << boolalpha;
    cout << "is_pointer:"
         << endl;
    cout << "GFG: "
         << is_pointer<GFG>::value << '\n';
    cout << "GFG*: "
         << is_pointer<GFG*>::value << '\n';
    cout << "GFG&: "
         << is_pointer<GFG&>::value << '\n';
    cout << "nullptr_t: "
         << is_pointer<nullptr_t>::value << '\n';
  
    return 0;
}
Output:
is_pointer:
GFG: false
GFG*: true
GFG&: false
nullptr_t: false

Program 2:




// C++ program to illustrate
// is_pointer template
  
#include <iostream>
#include <type_traits>
using namespace std;
  
// main program
int main()
{
    cout << boolalpha;
    cout << "is_pointer:"
         << endl;
    cout << "int: "
         << is_pointer<int>::value << '\n';
    cout << "int *: "
         << is_pointer<int*>::value << '\n';
    cout << "int **: "
         << is_pointer<int**>::value << '\n';
    cout << "int ***: "
         << is_pointer<int***>::value << '\n';
  
    return 0;
}
Output:
is_pointer:
int: false
int *: true
int **: true
int ***: true

Program 3:




// C++ program to illustrate
// is_pointer template
  
#include <iostream>
#include <type_traits>
using namespace std;
  
// main program
int main()
{
  
    cout << boolalpha;
    cout << "is_pointer:" << endl;
    cout << "int *&: "
         << is_pointer<int*&>::value << '\n';
    cout << "int *[10]: "
         << is_pointer<int * [10]>::value << '\n';
    cout << "float *: "
         << is_pointer<float*>::value << '\n';
    cout << "int[10]:"
         << is_pointer<int[10]>::value << '\n';
  
    return 0;
}
Output:
is_pointer:
int *&: false
int *[10]: false
float *: true
int[10]:false
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