std::is_pointer

From cppreference.com

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
Execution control library(C++26)
Technical specifications
Symbols index
External libraries

[edit]

Metaprogramming library

Type traits

Type categories

is_void

(C++11)

is_null_pointer

(C++11)(DR*)

is_array (C++11)
is_pointer (C++11)
is_enum (C++11)
is_union (C++11)
is_class (C++11)
is_function (C++11)
is_reference (C++11)

is_object (C++11)
is_scalar (C++11)
is_compound (C++11)
is_integral (C++11)
is_floating_point (C++11)
is_fundamental (C++11)
is_arithmetic (C++11)

is_lvalue_reference

(C++11)

is_rvalue_reference

(C++11)

is_member_pointer

(C++11)

is_member_object_pointer

(C++11)

is_member_function_pointer

(C++11)

Type properties

(C++11)

(C++11)

(C++11)

(C++11)

(C++14)

(C++11)

(C++17)

(C++23)

(C++11)(deprecated in C++26)

is_trivially_copyable

(C++11)

is_standard_layout

(C++11)

is_literal_type

(C++11)(until C++20*)

is_pod

(C++11)(deprecated in C++20)

(C++11)

(C++11)

(C++20)

(C++20)

(C++23)

has_unique_object_representations

(C++17)

Type trait constants

integral_constantbool_constanttrue_typefalse_type

(C++11)(C++17)(C++11)(C++11)

Metafunctions

conjunction

(C++17)

disjunction

(C++17)

negation

(C++17)

Supported operations

is_constructibleis_trivially_constructibleis_nothrow_constructible (C++11)(C++11)(C++11)
is_default_constructibleis_trivially_default_constructibleis_nothrow_default_constructible (C++11)(C++11)(C++11)
is_copy_constructibleis_trivially_copy_constructibleis_nothrow_copy_constructible (C++11)(C++11)(C++11)
is_move_constructibleis_trivially_move_constructibleis_nothrow_move_constructible (C++11)(C++11)(C++11)
is_assignableis_trivially_assignableis_nothrow_assignable (C++11)(C++11)(C++11)

is_copy_assignableis_trivially_copy_assignableis_nothrow_copy_assignable (C++11)(C++11)(C++11)
is_move_assignableis_trivially_move_assignableis_nothrow_move_assignable (C++11)(C++11)(C++11)
is_destructibleis_trivially_destructibleis_nothrow_destructible (C++11)(C++11)(C++11)
has_virtual_destructor (C++11)
is_swappable_withis_swappableis_nothrow_swappable_withis_nothrow_swappable (C++17)(C++17)(C++17)(C++17)

Relationships and property queries

is_same (C++11)
is_convertibleis_nothrow_convertible (C++11)(C++20)
is_layout_compatible (C++20)
is_pointer_interconvertible_base_of (C++20)
is_pointer_interconvertible_with_class (C++20)
is_corresponding_member (C++20)
reference_constructs_from_temporary (C++23)
reference_converts_from_temporary (C++23)

is_base_of (C++11)
is_virtual_base_of (C++26)
alignment_of (C++11)
rank (C++11)
extent (C++11)
is_invocableis_invocable_ris_nothrow_invocableis_nothrow_invocable_r (C++17)(C++17)(C++17)(C++17)

Type modifications

remove_cvremove_constremove_volatile (C++11)(C++11)(C++11)
add_cvadd_constadd_volatile (C++11)(C++11)(C++11)
make_signed (C++11)
make_unsigned (C++11)

remove_reference (C++11)
add_lvalue_referenceadd_rvalue_reference (C++11)(C++11)
remove_pointer (C++11)
add_pointer (C++11)
remove_extent (C++11)
remove_all_extents (C++11)

Type transformations

aligned_storage (C++11)(deprecated in C++23)
aligned_union (C++11)(deprecated in C++23)
decay (C++11)
remove_cvref (C++20)
result_ofinvoke_result (C++11)(until C++20*)(C++17)

conditional (C++11)
common_type (C++11)
common_reference (C++20)
underlying_type (C++11)
type_identity (C++20)
enable_if (C++11)
void_t (C++17)

Compile-time rational arithmetic

Compile-time integer sequences

integer_sequence

(C++14)

[edit]

Defined in header`<type_traits>`
template<class T> struct is_pointer;		(since C++11)

std::is_pointer is aUnaryTypeTrait.

Checks whetherT is apointer to object or function (including pointer tovoid, but excluding pointer to member) or a cv-qualified version thereof. Provides the member constantvalue which is equal totrue, ifT is an object/function pointer type. Otherwise,value is equal tofalse.

If the program adds specializations forstd::is_pointer orstd::is_pointer_v, the behavior is undefined.

[edit]Template parameters

a type to check

[edit]Helper variable template

template<class T> constexprbool is_pointer_v= is_pointer<T>::value;		(since C++17)

[edit]

Inherited fromstd::integral_constant

Member constants

value

[static]

true ifT is a pointer type,false otherwise
(public static member constant)

Member functions

operator bool	converts the object tobool, returnsvalue (public member function)
operator() (C++14)	returnsvalue (public member function)

Member types

Type	Definition
`value_type`	bool
`type`	std::integral_constant<bool, value>

[edit]Possible implementation

template<class T>struct is_pointer:std::false_type{}; template<class T>struct is_pointer<T*>:std::true_type{}; template<class T>struct is_pointer<T*const>:std::true_type{}; template<class T>struct is_pointer<T*volatile>:std::true_type{}; template<class T>struct is_pointer<T*constvolatile>:std::true_type{};

[edit]Example

Run this code

#include <type_traits> int main(){struct A{int m;void f(){}}; int A::*mem_data_ptr=&A::m;// a pointer to member datavoid(A::*mem_fun_ptr)()=&A::f;// a pointer to member function     static_assert(! std::is_pointer<A>::value&&! std::is_pointer_v<A>// same thing as above, but in C++17!&&! std::is_pointer<A>()// same as above, using inherited operator bool&&! std::is_pointer<A>{}// ditto&&! std::is_pointer<A>()()// same as above, using inherited operator()&&! std::is_pointer<A>{}()// ditto&&   std::is_pointer_v<A*>&&   std::is_pointer_v<Aconst*volatile>&&! std::is_pointer_v<A&>&&! std::is_pointer_v<decltype(mem_data_ptr)>&&! std::is_pointer_v<decltype(mem_fun_ptr)>&&   std::is_pointer_v<void*>&&! std::is_pointer_v<int>&&   std::is_pointer_v<int*>&&   std::is_pointer_v<int**>&&! std::is_pointer_v<int[10]>&&! std::is_pointer_v<std::nullptr_t>&&   std::is_pointer_v<void(*)()>);}

[edit]See also

is_member_pointer (C++11)	checks if a type is a pointer to a non-static member function or object (class template)[edit]
is_member_object_pointer (C++11)	checks if a type is a non-static member object pointer (class template)[edit]
is_member_function_pointer (C++11)	checks if a type is a non-static member function pointer (class template)[edit]
is_array (C++11)	checks if a type is an array type (class template)[edit]
is_scalar (C++11)	checks if a type is a scalar type (class template)[edit]