std::is_null_pointer

template <class T> struct is_null_pointer;

Is null pointer

integral_constant
is_null_pointer

Trait class that identifies whether the type of T is nullptr_t.

Note that this trait only classifies the type of T, not whether the potential value of a pointer is a null pointer value.

It inherits from integral_constant as being either true_type or false_type.

Template parameters

T: A type.

Member types

Inherited from integral_constant:

member type	definition
`value_type`	`bool`
`type`	either true_type or false_type

Member constants

Inherited from integral_constant:

member constant	definition
`value`	either `true` or `false`

Member functions

Inherited from integral_constant:

operator bool: Returns value (public member function )

Example

// is_null_pointer example
#include <iostream>
#include <type_traits>

int main() {
  int* a = 0;
  std::cout << std::boolalpha;
  std::cout << "is_null_pointer:\n";
  std::cout << "decltype(a): " << std::is_null_pointer<decltype(a)>::value << '\n';
  std::cout << "decltype(nullptr): " << std::is_null_pointer<decltype(nullptr)>::value << '\n';
  return 0;
}

Output:

is_pointer:
decltype(a): false
decltype(nullptr): true

std::is_null_pointer

Template parameters

Member types

Member constants

Member functions

Example

See also

C++

Reference

C library:

Containers:

Input/Output:

Multi-threading:

Other:

<type_traits>

helper classes:

type traits:

type transformations: