std::meta::rank

 

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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

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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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Defined in header <meta>
consteval std::size_t rank( std::meta::info r );		(since C++26)

Returns the number of dimensions of reflected array type represented by reflection r.

Equivalent to return std::rank<T>::value, where T is the type represented by std::meta::dealias(r).

Parameters

r

-

a reflection value

Return value

The number of dimensions of the array.

Exceptions

std::meta::exception if r does not represent an array type.

Example

Run this code

#include <meta>
#include <print>

static_assert(std::meta::rank(^^int) == 0);
static_assert(std::meta::rank(^^int[5]) == 1);
static_assert(std::meta::rank(^^int[5][5]) == 2);
static_assert(std::meta::rank(^^int[][5][5]) == 3);

int main()
{
    int a[][3]{ {1, 2, 3} };
    std::println("{}", a);

    // The rank of reference type, e.g., a[0], that is int(&)[3], is 0:
    static_assert(std::meta::rank(^^decltype(a[0])) == 0);
    static_assert(std::meta::is_same_type(^^decltype(a[0]), ^^int(&)[3]));

    // The solution is to remove the reference type.
    static_assert(std::meta::rank(std::meta::remove_cvref(^^decltype(a[0]))) == 1);
}

Output:

[[1, 2, 3]]

See also

is_array_type (C++26)	checks if reflected type is an array type (function)
extent (C++26)	obtains the size of reflected array type along a specified dimension (function)
remove_extent (C++26)	removes one extent from reflected array type (function)
remove_all_extents (C++26)	removes all extents from reflected array type (function)
rank (C++11)	obtains the number of dimensions of an array type (class template)