std::meta::is_same_type

 

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Checking string literals is_string_literal Types info meta::exception access_context data_member_options member_offset operators Concepts reflection_range Promoting to static storage reflect_constant_string reflect_constant_array define_static_string define_static_array define_static_object Operator representations operator_of symbol_of u8symbol_of Names and locations has_identifier identifier_of u8identifier_of display_string_of u8display_string_of source_location_of Reflection queries ➜ Member accessibility queries is_accessible has_inaccessible_nonstatic_   data_members has_inaccessible_bases has_inaccessible_subobjects

Scope identification current_function current_class current_namespace Reflection member queries members_of bases_of static_data_members_of nonstatic_data_members_of      subobjects_of enumerators_of Reflection layout queries offset_of size_of alignment_of bit_size_of Annotation reflection annotations_of annotations_of_with_type Value extraction extract Reflection substitution can_substitute substitute Expression result reflection reflect_constant reflect_object reflect_function Class definition generation data_member_spec is_data_member_spec define_aggregate

Primary type categories is_void_type is_null_pointer_type is_integral_type is_floating_point_type is_array_type is_pointer_type is_lvalue_reference_type is_rvalue_reference_type is_member_object_pointer_type is_member_function_pointer_type      is_enum_type is_union_type is_class_type is_function_type is_reflection_type Composite type categories is_reference_type is_arithmetic_type is_fundamental_type is_object_type is_scalar_type is_compound_type is_member_pointer_type Type properties ➜ Type relations is_same_type is_base_of_type is_virtual_base_of_type is_convertible_type is_nothrow_convertible_type is_layout_compatible_type is_pointer_interconvertible_   base_of_type is_invocable_type is_invocable_r_type is_nothrow_invocable_type is_nothrow_invocable_r_type

Const-volatile modifications remove_const remove_volatile remove_cv add_const add_volatile add_cv Reference modifications remove_reference add_lvalue_reference add_rvalue_reference Sign modifications make_signed make_unsigned Array modifications remove_extent remove_all_extents Pointer modifications remove_pointer add_pointer Other transformations remove_cvref decay common_type common_reference underlying_type invoke_result unwrap_reference unwrap_ref_decay tuple_size tuple_element is_applicable_type is_nothrow_applicable_type apply_result variant_size variant_alternative type_order

 

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Reflection queries type_of object_of constant_of is_public is_protected is_private is_virtual is_pure_virtual is_override is_final is_deleted is_defaulted is_user_provided is_user_declared is_explicit is_noexcept is_bit_field is_enumerator is_annotation is_const is_volatile is_mutable_member is_lvalue_reference_qualified is_rvalue_reference_qualified has_static_storage_duration has_thread_storage_duration has_automatic_storage_duration      has_internal_linkage has_module_linkage has_external_linkage has_linkage has_c_language_linkage is_complete_type is_enumerable_type is_variable is_type is_namespace is_type_alias is_namespace_alias is_function is_conversion_function is_operator_function is_literal_operator is_special_member_function is_destructor

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is_polymorphic_type is_abstract_type is_final_type is_aggregate_type is_structural_type is_signed_type is_unsigned_type is_bounded_array_type is_unbounded_array_type is_scoped_enum_type is_constructible_type is_trivially_constructible_type is_nothrow_constructible_type is_default_constructible_type is_trivially_default_constructible_type is_nothrow_default_constructible_type is_copy_constructible_type is_trivially_copy_constructible_type is_nothrow_copy_constructible_type is_move_constructible_type is_trivially_move_constructible_type is_nothrow_move_constructible_type is_assignable_type is_trivially_assignable_type is_nothrow_assignable_type is_copy_assignable_type is_trivially_copy_assignable_type is_nothrow_copy_assignable_type is_move_assignable_type is_trivially_move_assignable_type is_nothrow_move_assignable_type is_swappable_with_type is_swappable_type is_nothrow_swappable_with_type is_nothrow_swappable_type is_destructible_type is_trivially_destructible_type is_nothrow_destructible_type is_implicit_lifetime_type has_virtual_destructor has_unique_object_representations reference_constructs_from_temporary reference_converts_from_temporary Type property queries rank extent

 

Defined in header <meta>
consteval bool is_same_type( std::meta::info r1, std::meta::info r2 );		(since C++26)

If two reflections r1 and r2 represent the same type (taking into account cv-qualifications), returns true. Otherwise, returns false.

Commutativity is satisfied, i.e., for any two reflections:

is_same_type(r1, r2) == true if and only if

is_same_type(r2, r1) == true.

Parameters

r1, r2

-

reflections to compare

Return value

true if r1 and r2 represent the same type, false otherwise.

Exceptions

Throws std::meta::exception if either r1 or r2 does not represent a type or type alias.

Notes

If r1 is a reflection of the type int and r2 is a reflection of an alias to the type int, then r1 == r2 is false but std::meta::is_same_type(r1, r2) is true. Also, r1 == std::meta::dealias(r2) is true.

Example

Run this code

#include <cstdint>
#include <meta>
#include <print>

constexpr long double num1{1.0};
constexpr long double num2{2.0};

static_assert
(""
    // compare the types of a couple variables
    && is_same_type(^^decltype(num1), ^^decltype(num2))

    // ‘float’ is never an integral type
    && !is_same_type(^^float, ^^int32_t)

    // ‘int’ is implicitly ‘signed’
    && is_same_type(^^int, ^^int)
    && !is_same_type(^^int, ^^unsigned int)
    && is_same_type(^^int, ^^signed int)

    // unlike other types, ‘char’ is neither ‘unsigned’ nor ‘signed’
    && is_same_type(^^char, ^^char)
    && !is_same_type(^^char, ^^unsigned char)
    && !is_same_type(^^char, ^^signed char)

    // const-qualified type T is not same as non-const T
    && !is_same_type(^^const int, ^^int)
);

#define SHOW(...) std::println("{} == {}", #__VA_ARGS__, __VA_ARGS__)

int main()
{
    // Some implementation-defined facts:

    // usually true if ‘int’ is 32 bit
    SHOW(is_same_type(^^int, std::meta::dealias(^^int32_t))); // maybe true

    // possibly true if ILP64 data model is used
    SHOW(is_same_type(^^int, std::meta::dealias(^^int64_t))); // maybe false
}

Possible output:

is_same_type(^^int, std::meta::dealias(^^int32_t)) == true
is_same_type(^^int, std::meta::dealias(^^int64_t)) == false

See also

decltype specifier(C++11)	obtains the type of an expression or an entity
is_type (C++26)	checks if reflection represents a type (function)
same_as (C++20)	specifies that a type is the same as another type (concept)
is_same (C++11)	checks if two types are the same (class template)