101 KiB
[support.limits]
17 Language support library [support]
17.3 Implementation properties [support.limits]
17.3.1 General [support.limits.general]
The headers,, and supply characteristics ofimplementation-dependent arithmetic types ([basic.fundamental]).
17.3.2 Header synopsis [version.syn]
The header supplies implementation-dependent information about the C++ standard library (e.g., version number and release date).
Each of the macros defined in is also defined after inclusion of any member of the set of library headers indicated in the corresponding comment in this synopsis.
[Note 1:
Future revisions of this document might replace the values of these macros with greater values.
â end note]
#define __cpp_lib_adaptor_iterator_pair_constructor 202106L // also in , #define __cpp_lib_addressof_constexpr 201603L // freestanding, also in #define __cpp_lib_algorithm_default_value_type 202403L// also in , , , , , <forward_list>, #define __cpp_lib_algorithm_iterator_requirements 202207L// also in , , #define __cpp_lib_aligned_accessor 202411L // also in #define __cpp_lib_allocate_at_least 202302L // also in #define __cpp_lib_allocator_traits_is_always_equal 201411L// freestanding, also in , <scoped_allocator>, , , <forward_list>, ,// , , , <unordered_map>, <unordered_set>#define __cpp_lib_any 201606L // also in #define __cpp_lib_apply 202506L // freestanding, also in , <type_traits>#define __cpp_lib_array_constexpr 201811L // also in , #define __cpp_lib_as_const 201510L // freestanding, also in #define __cpp_lib_associative_heterogeneous_erasure 202110L// also in , , <unordered_map>, <unordered_set>#define __cpp_lib_associative_heterogeneous_insertion 202306L// also in , , <unordered_map>, <unordered_set>#define __cpp_lib_assume_aligned 201811L // freestanding, also in #define __cpp_lib_atomic_flag_test 201907L // freestanding, also in #define __cpp_lib_atomic_float 201711L // freestanding, also in #define __cpp_lib_atomic_is_always_lock_free 201603L // freestanding, also in #define __cpp_lib_atomic_lock_free_type_aliases 201907L // also in #define __cpp_lib_atomic_min_max 202506L // freestanding, also in #define __cpp_lib_atomic_reductions 202506L // freestanding, also in #define __cpp_lib_atomic_ref 202411L // freestanding, also in #define __cpp_lib_atomic_shared_ptr 201711L // also in #define __cpp_lib_atomic_value_initialization 201911L // freestanding, also in , #define __cpp_lib_atomic_wait 201907L // freestanding, also in #define __cpp_lib_barrier 202302L // also in #define __cpp_lib_bind_back 202306L // freestanding, also in #define __cpp_lib_bind_front 202306L // freestanding, also in #define __cpp_lib_bit_cast 201806L // freestanding, also in #define __cpp_lib_bitops 201907L // freestanding, also in #define __cpp_lib_bitset 202306L // also in #define __cpp_lib_bool_constant 201505L // freestanding, also in <type_traits>#define __cpp_lib_bounded_array_traits 201902L // freestanding, also in <type_traits>#define __cpp_lib_boyer_moore_searcher 201603L // also in #define __cpp_lib_byte 201603L // freestanding, also in #define __cpp_lib_byteswap 202110L // freestanding, also in #define __cpp_lib_char8_t 201907L// freestanding, also in , , , , , , ,// <string_view>#define __cpp_lib_chrono 202306L // also in #define __cpp_lib_chrono_udls 201304L // also in #define __cpp_lib_clamp 201603L // also in #define __cpp_lib_common_reference 202302L // freestanding, also in <type_traits>#define __cpp_lib_common_reference_wrapper 202302L // freestanding, also in #define __cpp_lib_complex_udls 201309L // also in #define __cpp_lib_concepts 202207L// freestanding, also in , #define __cpp_lib_constant_wrapper 202506L // freestanding, also in <type_traits>#define __cpp_lib_constexpr_algorithms 202306L // also in , #define __cpp_lib_constexpr_atomic 202411L // also in #define __cpp_lib_constexpr_bitset 202207L // also in #define __cpp_lib_constexpr_charconv 202207L // freestanding, also in #define __cpp_lib_constexpr_cmath 202306L // also in , #define __cpp_lib_constexpr_complex 202306L // also in #define __cpp_lib_constexpr_deque 202502L // also in #define __cpp_lib_constexpr_dynamic_alloc 201907L // also in #define __cpp_lib_constexpr_exceptions 202502L// also in , , , , , and #define __cpp_lib_constexpr_flat_map 202502L // also in <flat_map>#define __cpp_lib_constexpr_flat_set 202502L // also in <flat_set>#define __cpp_lib_constexpr_forward_list 202502L // also in <forward_list>#define __cpp_lib_constexpr_functional 201907L // freestanding, also in #define __cpp_lib_constexpr_inplace_vector 202502L // also in <inplace_vector>#define __cpp_lib_constexpr_iterator 201811L // freestanding, also in #define __cpp_lib_constexpr_list 202502L // also in #define __cpp_lib_constexpr_map 202502L // also in #define __cpp_lib_constexpr_memory 202506L // freestanding, also in #define __cpp_lib_constexpr_new 202406L // freestanding, also in #define __cpp_lib_constexpr_numeric 201911L // also in #define __cpp_lib_constexpr_queue 202502L // also in #define __cpp_lib_constexpr_set 202502L // also in #define __cpp_lib_constexpr_stack 202502L // also in #define __cpp_lib_constexpr_string 201907L // also in #define __cpp_lib_constexpr_string_view 201811L // also in <string_view>#define __cpp_lib_constexpr_tuple 201811L // freestanding, also in #define __cpp_lib_constexpr_typeinfo 202106L // freestanding, also in #define __cpp_lib_constexpr_unordered_map 202502L // also in <unordered_map>#define __cpp_lib_constexpr_unordered_set 202502L // also in <unordered_set>#define __cpp_lib_constexpr_utility 201811L // freestanding, also in #define __cpp_lib_constexpr_vector 201907L // also in #define __cpp_lib_constrained_equality 202411L // freestanding,// also in , , , , #define __cpp_lib_containers_ranges 202202L// also in , , <forward_list>, , , <unordered_map>, <unordered_set>,// , , , #define __cpp_lib_contracts 202502L // freestanding, also in #define __cpp_lib_copyable_function 202306L // also in #define __cpp_lib_coroutine 201902L // freestanding, also in #define __cpp_lib_counting_scope 202506L // also in #define __cpp_lib_debugging 202403L // freestanding, also in #define __cpp_lib_define_static 202506L // freestanding, also in #define __cpp_lib_destroying_delete 201806L // freestanding, also in #define __cpp_lib_enable_shared_from_this 201603L // also in #define __cpp_lib_endian 201907L // freestanding, also in #define __cpp_lib_erase_if 202002L// also in , , <forward_list>, , , , , <unordered_map>,// <unordered_set>#define __cpp_lib_exception_ptr_cast 202506L // also in #define __cpp_lib_exchange_function 201304L // freestanding, also in #define __cpp_lib_execution 201902L // also in #define __cpp_lib_expected 202211L // also in #define __cpp_lib_filesystem 201703L // also in #define __cpp_lib_flat_map 202207L // also in <flat_map>#define __cpp_lib_flat_set 202207L // also in <flat_set>#define __cpp_lib_format 202311L // also in #define __cpp_lib_format_ranges 202207L // also in #define __cpp_lib_format_path 202506L // also in #define __cpp_lib_format_uchar 202311L // also in #define __cpp_lib_formatters 202302L // also in , #define __cpp_lib_forward_like 202207L // freestanding, also in #define __cpp_lib_freestanding_algorithm 202502L // freestanding, also in #define __cpp_lib_freestanding_array 202311L // freestanding, also in #define __cpp_lib_freestanding_char_traits 202306L // freestanding, also in #define __cpp_lib_freestanding_charconv 202306L // freestanding, also in #define __cpp_lib_freestanding_cstdlib 202306L // freestanding, also in , #define __cpp_lib_freestanding_cstring 202311L // freestanding, also in #define __cpp_lib_freestanding_cwchar 202306L // freestanding, also in #define __cpp_lib_freestanding_errc 202306L// freestanding, also in , <system_error>#define __cpp_lib_freestanding_execution 202502L // freestanding, also in #define __cpp_lib_freestanding_expected 202311L // freestanding, also in #define __cpp_lib_freestanding_feature_test_macros 202306L // freestanding#define __cpp_lib_freestanding_functional 202306L // freestanding, also in #define __cpp_lib_freestanding_iterator 202306L // freestanding, also in #define __cpp_lib_freestanding_mdspan 202311L // freestanding, also in #define __cpp_lib_freestanding_memory 202502L // freestanding, also in #define __cpp_lib_freestanding_numeric 202502L // freestanding, also in #define __cpp_lib_freestanding_operator_new see below // freestanding, also in #define __cpp_lib_freestanding_optional 202506L // freestanding, also in #define __cpp_lib_freestanding_random 202502L // freestanding, also in #define __cpp_lib_freestanding_ranges 202306L // freestanding, also in #define __cpp_lib_freestanding_ratio 202306L // freestanding, also in #define __cpp_lib_freestanding_string_view 202311L // freestanding, also in <string_view>#define __cpp_lib_freestanding_tuple 202306L // freestanding, also in #define __cpp_lib_freestanding_utility 202306L // freestanding, also in #define __cpp_lib_freestanding_variant 202311L // freestanding, also in #define __cpp_lib_fstream_native_handle 202306L // also in #define __cpp_lib_function_ref 202306L // also in #define __cpp_lib_gcd_lcm 201606L // also in #define __cpp_lib_generator 202207L // also in #define __cpp_lib_generic_associative_lookup 201304L // also in , #define __cpp_lib_generic_unordered_lookup 201811L// also in <unordered_map>, <unordered_set>#define __cpp_lib_hardware_interference_size 201703L // freestanding, also in #define __cpp_lib_has_unique_object_representations 201606L // freestanding, also in <type_traits>#define __cpp_lib_hazard_pointer 202306L // also in <hazard_pointer>#define __cpp_lib_hive 202502L // also in #define __cpp_lib_hypot 201603L // also in #define __cpp_lib_incomplete_container_elements 201505L// also in <forward_list>, , #define __cpp_lib_indirect 202502L // also in #define __cpp_lib_inplace_vector 202406L // also in <inplace_vector>#define __cpp_lib_int_pow2 202002L // freestanding, also in #define __cpp_lib_integer_comparison_functions 202002L // also in #define __cpp_lib_integer_sequence 201304L // freestanding, also in #define __cpp_lib_integral_constant_callable 201304L // freestanding, also in <type_traits>#define __cpp_lib_interpolate 201902L // also in , #define __cpp_lib_invoke 201411L // freestanding, also in #define __cpp_lib_invoke_r 202106L // freestanding, also in #define __cpp_lib_ios_noreplace 202207L // also in #define __cpp_lib_is_aggregate 201703L // freestanding, also in <type_traits>#define __cpp_lib_is_constant_evaluated 201811L // freestanding, also in <type_traits>#define __cpp_lib_is_final 201402L // freestanding, also in <type_traits>#define __cpp_lib_is_implicit_lifetime 202302L // freestanding, also in <type_traits>#define __cpp_lib_is_invocable 201703L // freestanding, also in <type_traits>#define __cpp_lib_is_layout_compatible 201907L // freestanding, also in <type_traits>#define __cpp_lib_is_nothrow_convertible 201806L // freestanding, also in <type_traits>#define __cpp_lib_is_null_pointer 201309L // freestanding, also in <type_traits>#define __cpp_lib_is_pointer_interconvertible 201907L // freestanding, also in <type_traits>#define __cpp_lib_is_scoped_enum 202011L // freestanding, also in <type_traits>#define __cpp_lib_is_sufficiently_aligned 202411L // also in #define __cpp_lib_is_swappable 201603L // freestanding, also in <type_traits>#define __cpp_lib_is_virtual_base_of 202406L // freestanding, also in <type_traits>#define __cpp_lib_is_within_lifetime 202306L // freestanding, also in <type_traits>#define __cpp_lib_jthread 201911L // also in <stop_token>, #define __cpp_lib_latch 201907L // also in #define __cpp_lib_launder 201606L // freestanding, also in #define __cpp_lib_linalg 202412L // also in #define __cpp_lib_list_remove_return_type 201806L // also in <forward_list>, #define __cpp_lib_logical_traits 201510L // freestanding, also in <type_traits>#define __cpp_lib_make_from_tuple 201606L // freestanding, also in #define __cpp_lib_make_reverse_iterator 201402L // freestanding, also in #define __cpp_lib_make_unique 201304L // also in #define __cpp_lib_map_try_emplace 201411L // also in #define __cpp_lib_math_constants 201907L // also in #define __cpp_lib_math_special_functions 201603L // also in #define __cpp_lib_mdspan 202406L // freestanding, also in #define __cpp_lib_memory_resource 201603L // also in <memory_resource>#define __cpp_lib_modules 202207L // freestanding#define __cpp_lib_move_iterator_concept 202207L // freestanding, also in #define __cpp_lib_move_only_function 202110L // also in #define __cpp_lib_node_extract 201606L// also in , , <unordered_map>, <unordered_set>#define __cpp_lib_nonmember_container_access 201411L// freestanding, also in , , <forward_list>, , , , , ,// , <unordered_map>, <unordered_set>, #define __cpp_lib_not_fn 202306L // freestanding, also in #define __cpp_lib_null_iterators 201304L // freestanding, also in #define __cpp_lib_observable_checkpoint 202506L // freestanding, also in #define __cpp_lib_optional 202506L // also in #define __cpp_lib_optional_range_support 202406L // freestanding, also in #define __cpp_lib_out_ptr 202311L // freestanding, also in #define __cpp_lib_parallel_algorithm 202506L// also in , , #define __cpp_lib_parallel_scheduler 202506L // also in #define __cpp_lib_philox_engine 202406L // also in #define __cpp_lib_polymorphic 202502L // also in #define __cpp_lib_polymorphic_allocator 201902L // also in <memory_resource>#define __cpp_lib_print 202406L // also in , #define __cpp_lib_quoted_string_io 201304L // also in #define __cpp_lib_ranges 202406L// also in , , , , #define __cpp_lib_ranges_as_const 202311L // freestanding, also in #define __cpp_lib_ranges_as_rvalue 202207L // freestanding, also in #define __cpp_lib_ranges_cache_latest 202411L // freestanding, also in #define __cpp_lib_ranges_cartesian_product 202207L // freestanding, also in #define __cpp_lib_ranges_chunk 202202L // freestanding, also in #define __cpp_lib_ranges_chunk_by 202202L // freestanding, also in #define __cpp_lib_ranges_concat 202403L // freestanding, also in #define __cpp_lib_ranges_contains 202207L // also in #define __cpp_lib_ranges_enumerate 202302L // also in #define __cpp_lib_ranges_find_last 202207L // also in #define __cpp_lib_ranges_fold 202207L // also in #define __cpp_lib_ranges_generate_random 202403L // also in #define __cpp_lib_ranges_indices 202506L // also in #define __cpp_lib_ranges_iota 202202L // also in #define __cpp_lib_ranges_join_with 202202L // freestanding, also in #define __cpp_lib_ranges_repeat 202207L // freestanding, also in #define __cpp_lib_ranges_reserve_hint 202502L // also in #define __cpp_lib_ranges_slide 202202L // freestanding, also in #define __cpp_lib_ranges_starts_ends_with 202106L // also in #define __cpp_lib_ranges_stride 202207L // freestanding, also in #define __cpp_lib_ranges_to_container 202202L // freestanding, also in #define __cpp_lib_ranges_to_input 202502L // freestanding, also in #define __cpp_lib_ranges_zip 202110L// freestanding, also in , , #define __cpp_lib_ratio 202306L // freestanding, also in #define __cpp_lib_raw_memory_algorithms 202411L // also in #define __cpp_lib_rcu 202306L // also in #define __cpp_lib_reference_from_temporary 202202L // freestanding, also in <type_traits>#define __cpp_lib_reference_wrapper 202403L // freestanding, also in #define __cpp_lib_reflection 202506L // also in #define __cpp_lib_remove_cvref 201711L // freestanding, also in <type_traits>#define __cpp_lib_result_of_sfinae 201210L// freestanding, also in , <type_traits>#define __cpp_lib_robust_nonmodifying_seq_ops 201304L // also in #define __cpp_lib_sample 201603L // also in #define __cpp_lib_saturation_arithmetic 202311L // also in #define __cpp_lib_scoped_lock 201703L // also in #define __cpp_lib_semaphore 201907L // also in #define __cpp_lib_senders 202506L // also in #define __cpp_lib_shared_mutex 201505L // also in <shared_mutex>#define __cpp_lib_shared_ptr_arrays 201707L // also in #define __cpp_lib_shared_ptr_weak_type 201606L // also in #define __cpp_lib_shared_timed_mutex 201402L // also in <shared_mutex>#define __cpp_lib_shift 202202L // also in #define __cpp_lib_simd 202506L // also in #define __cpp_lib_simd_complex 202502L // also in #define __cpp_lib_simd_permutations 202506L // also in #define __cpp_lib_smart_ptr_for_overwrite 202002L // also in #define __cpp_lib_smart_ptr_owner_equality 202306L // also in #define __cpp_lib_source_location 201907L // freestanding, also in <source_location>#define __cpp_lib_span 202311L // freestanding, also in #define __cpp_lib_span_initializer_list 202311L // freestanding, also in #define __cpp_lib_spanstream 202106L // also in #define __cpp_lib_ssize 201902L // freestanding, also in #define __cpp_lib_sstream_from_string_view 202306L // also in #define __cpp_lib_stacktrace 202011L // also in #define __cpp_lib_start_lifetime_as 202207L // freestanding, also in #define __cpp_lib_starts_ends_with 201711L // also in , <string_view>#define __cpp_lib_stdatomic_h 202011L // also in <stdatomic.h>#define __cpp_lib_string_contains 202011L // also in , <string_view>#define __cpp_lib_string_resize_and_overwrite 202110L // also in #define __cpp_lib_string_subview 202506L // also in , <string_view>#define __cpp_lib_string_udls 201304L // also in #define __cpp_lib_string_view 202403L // also in , <string_view>#define __cpp_lib_submdspan 202411L // freestanding, also in #define __cpp_lib_syncbuf 201803L // also in #define __cpp_lib_task 202506L // also in #define __cpp_lib_text_encoding 202306L // also in <text_encoding>#define __cpp_lib_three_way_comparison 201907L // freestanding, also in #define __cpp_lib_to_address 201711L // freestanding, also in #define __cpp_lib_to_array 201907L // freestanding, also in #define __cpp_lib_to_chars 202306L // also in #define __cpp_lib_to_string 202306L // also in #define __cpp_lib_to_underlying 202102L // freestanding, also in #define __cpp_lib_transformation_trait_aliases 201304L // freestanding, also in <type_traits>#define __cpp_lib_transparent_operators 201510L// freestanding, also in , #define __cpp_lib_trivially_relocatable 202502L// freestanding, also in , <type_traits>#define __cpp_lib_tuple_element_t 201402L // freestanding, also in #define __cpp_lib_tuple_like 202311L// also in , , , <unordered_map>#define __cpp_lib_tuples_by_type 201304L // freestanding, also in , #define __cpp_lib_type_identity 201806L // freestanding, also in <type_traits>#define __cpp_lib_type_order 202506L // also in #define __cpp_lib_type_trait_variable_templates 201510L // freestanding, also in <type_traits>#define __cpp_lib_uncaught_exceptions 201411L // freestanding, also in #define __cpp_lib_unordered_map_try_emplace 201411L // also in <unordered_map>#define __cpp_lib_unreachable 202202L // freestanding, also in #define __cpp_lib_unwrap_ref 201811L // freestanding, also in <type_traits>#define __cpp_lib_variant 202306L // also in #define __cpp_lib_void_t 201411L // freestanding, also in <type_traits>
Additionally, each of the following macros is defined in a hardened implementation:#define __cpp_lib_hardened_array 202502L // also in #define __cpp_lib_hardened_basic_stacktrace 202506L // also in #define __cpp_lib_hardened_basic_string 202502L // also in #define __cpp_lib_hardened_basic_string_view 202502L // also in <string_view>#define __cpp_lib_hardened_bitset 202502L // also in #define __cpp_lib_hardened_common_iterator 202506L // also in #define __cpp_lib_hardened_counted_iterator 202506L // also in #define __cpp_lib_hardened_deque 202502L // also in #define __cpp_lib_hardened_expected 202502L // also in #define __cpp_lib_hardened_forward_list 202502L // also in <forward_list>#define __cpp_lib_hardened_inplace_vector 202502L // also in <inplace_vector>#define __cpp_lib_hardened_list 202502L // also in #define __cpp_lib_hardened_mdspan 202502L // also in #define __cpp_lib_hardened_optional 202502L // also in #define __cpp_lib_hardened_shared_ptr_array 202506L // also in #define __cpp_lib_hardened_span 202502L // also in #define __cpp_lib_hardened_valarray 202502L // also in #define __cpp_lib_hardened_vector 202502L // also in #define __cpp_lib_hardened_view_interface 202506L // also in
The macro __cpp_lib_freestanding_operator_new is defined to the integer literal 202306L if all the default versions of the replaceable global allocation functions meet the requirements of a hosted implementation, and to the integer literal 0 otherwise ([new.delete]).
Recommended practice: Freestanding implementations should only define a macro from if the implementation provides the corresponding facility in its entirety.
Recommended practice: A non-hardened implementation should not define macros from required for hardened implementations.
17.3.3 Header synopsis [limits.syn]
// all freestandingnamespace std {// [round.style], enumeration float_round_styleenum float_round_style; // [numeric.limits], class template numeric_limitstemplate class numeric_limits; template class numeric_limits; template class numeric_limits; template class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits<char8_t>; template<> class numeric_limits<char16_t>; template<> class numeric_limits<char32_t>; template<> class numeric_limits<wchar_t>; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits; template<> class numeric_limits;}
17.3.4 Enum float_round_style [round.style]
namespace std {enum float_round_style { round_indeterminate = -1, round_toward_zero = 0, round_to_nearest = 1, round_toward_infinity = 2, round_toward_neg_infinity = 3};}
The rounding mode for floating-point arithmetic is characterized by the values:
round_indeterminate if the rounding style is indeterminable
round_toward_zero if the rounding style is toward zero
round_to_nearest if the rounding style is to the nearest representable value
round_toward_infinity if the rounding style is toward infinity
round_toward_neg_infinity if the rounding style is toward negative infinity
17.3.5 Class template numeric_limits [numeric.limits]
17.3.5.1 General [numeric.limits.general]
Thenumeric_limits class template provides a C++ program with information about various properties of the implementation's representation of the arithmetic types.
namespace std {template class numeric_limits {public:static constexpr bool is_specialized = false; static constexpr T min() noexcept { return T(); }static constexpr T max() noexcept { return T(); }static constexpr T lowest() noexcept { return T(); }static constexpr int digits = 0; static constexpr int digits10 = 0; static constexpr int max_digits10 = 0; static constexpr bool is_signed = false; static constexpr bool is_integer = false; static constexpr bool is_exact = false; static constexpr int radix = 0; static constexpr T epsilon() noexcept { return T(); }static constexpr T round_error() noexcept { return T(); }static constexpr int min_exponent = 0; static constexpr int min_exponent10 = 0; static constexpr int max_exponent = 0; static constexpr int max_exponent10 = 0; static constexpr bool has_infinity = false; static constexpr bool has_quiet_NaN = false; static constexpr bool has_signaling_NaN = false; static constexpr T infinity() noexcept { return T(); }static constexpr T quiet_NaN() noexcept { return T(); }static constexpr T signaling_NaN() noexcept { return T(); }static constexpr T denorm_min() noexcept { return T(); }static constexpr bool is_iec559 = false; static constexpr bool is_bounded = false; static constexpr bool is_modulo = false; static constexpr bool traps = false; static constexpr bool tinyness_before = false; static constexpr float_round_style round_style = round_toward_zero; };}
For all members declaredstatic constexpr in thenumeric_limits template, specializations shall define these values in such a way that they are usable as constant expressions.
For thenumeric_limits primary template, all data members are value-initialized and all member functions return a value-initialized object.
[Note 1:
This means all members have zero or false values unless numeric_limits is specialized for a type.
â end note]
Specializations shall be provided for each arithmetic type, both floating-point and integer, includingbool.
The memberis_specialized shall betrue for all such specializations ofnumeric_limits.
The value of each member of a specialization ofnumeric_limits on a cv-qualified typecv T shall be equal to the value of the corresponding member of the specialization on the unqualified type T.
Non-arithmetic standard types, such ascomplex, shall not have specializations.
17.3.5.2 numeric_limits members [numeric.limits.members]
Each member function defined in this subclause is signal-safe ([support.signal]).
[Note 1:
The arithmetic specification described in ISO/IEC 10967-1:2012 is commonly termed LIA-1.
â end note]
static constexpr T min() noexcept;
For floating-point types with subnormal numbers, returns the minimum positive normalized value.
Meaningful for all specializations in whichis_bounded != false, oris_bounded == false && is_signed == false.
static constexpr T max() noexcept;
Meaningful for all specializations in whichis_bounded != false.
static constexpr T lowest() noexcept;
A finite value x such that there is no other finite value y where y < x.163
Meaningful for all specializations in which is_bounded != false.
static constexpr int digits;
Number ofradix digits that can be represented without change.
For integer types, the number of non-sign bits in the representation.
For floating-point types, the number of radix digits in the significand.164
static constexpr int digits10;
Number of base 10 digits that can be represented without change.165
Meaningful for all specializations in whichis_bounded != false.
static constexpr int max_digits10;
Number of base 10 digits required to ensure that values which differ are always differentiated.
Meaningful for all floating-point types.
static constexpr bool is_signed;
true if the type is signed.
Meaningful for all specializations.
static constexpr bool is_integer;
true if the type is integer.
Meaningful for all specializations.
static constexpr bool is_exact;
true if the type uses an exact representation.
All integer types are exact, but not all exact types are integer.
For example, rational and fixed-exponent representations are exact but not integer.
Meaningful for all specializations.
static constexpr int radix;
For floating-point types, specifies the base or radix of the exponent representation (often 2).166
For integer types, specifies the base of the representation.167
Meaningful for all specializations.
static constexpr T epsilon() noexcept;
Machine epsilon: the difference between 1 and the least value greater than 1 that is representable.168
Meaningful for all floating-point types.
static constexpr T round_error() noexcept;
Measure of the maximum rounding error.169
static constexpr int min_exponent;
Minimum negative integer such thatradix raised to the power of one less than that integer is a normalized floating-point number.170
Meaningful for all floating-point types.
static constexpr int min_exponent10;
Minimum negative integer such that 10 raised to that power is in the range of normalized floating-point numbers.171
Meaningful for all floating-point types.
static constexpr int max_exponent;
Maximum positive integer such thatradix raised to the power one less than that integer is a representable finite floating-point number.172
Meaningful for all floating-point types.
static constexpr int max_exponent10;
Maximum positive integer such that 10 raised to that power is in the range of representable finite floating-point numbers.173
Meaningful for all floating-point types.
static constexpr bool has_infinity;
true if the type has a representation for positive infinity.
Meaningful for all floating-point types.
Shall betrue for all specializations in whichis_iec559 != false.
static constexpr bool has_quiet_NaN;
true if the type has a representation for a quiet (non-signaling) âNot a Numberâ.174
Meaningful for all floating-point types.
Shall betrue for all specializations in whichis_iec559 != false.
static constexpr bool has_signaling_NaN;
true if the type has a representation for a signaling âNot a Numberâ.175
Meaningful for all floating-point types.
Shall betrue for all specializations in whichis_iec559 != false.
static constexpr T infinity() noexcept;
Representation of positive infinity, if available.176
Meaningful for all specializations for whichhas_infinity != false.
Required in specializations for whichis_iec559 != false.
static constexpr T quiet_NaN() noexcept;
Representation of a quiet âNot a Numberâ, if available.177
Meaningful for all specializations for whichhas_quiet_NaN != false.
Required in specializations for whichis_iec559 != false.
static constexpr T signaling_NaN() noexcept;
Representation of a signaling âNot a Numberâ, if available.178
Meaningful for all specializations for whichhas_signaling_NaN != false.
Required in specializations for whichis_iec559 != false.
static constexpr T denorm_min() noexcept;
Minimum positive subnormal value, if available.179
Otherwise, minimum positive normalized value.
Meaningful for all floating-point types.
static constexpr bool is_iec559;
true if and only if the type adheres to ISO/IEC 60559.180
[Note 2:
The value is true for any of the typesfloat16_t, float32_t, float64_t, or float128_t, if present ([basic.extended.fp]).
â end note]
Meaningful for all floating-point types.
static constexpr bool is_bounded;
true if the set of values representable by the type is finite.181
[Note 3:
All fundamental types ([basic.fundamental]) are bounded.
This member would be false for arbitrary precision types.
â end note]
Meaningful for all specializations.
static constexpr bool is_modulo;
true if the type is modulo.182
A type is modulo if, for any operation involving +, -, or* on values of that type whose result would fall outside the range [min(), max()], the value returned differs from the true value by an integer multiple of max() - min() + 1.
[Example 1:
is_modulo is false for signed integer types ([basic.fundamental]) unless an implementation, as an extension to this document, defines signed integer overflow to wrap.
â end example]
Meaningful for all specializations.
static constexpr bool traps;
true if, at the start of the program, there exists a value of the type that would cause an arithmetic operation using that value to trap.183
Meaningful for all specializations.
static constexpr bool tinyness_before;
true if tinyness is detected before rounding.184
Meaningful for all floating-point types.
static constexpr float_round_style round_style;
The rounding style for the type.185
Meaningful for all floating-point types.
Specializations for integer types shall returnround_toward_zero.
Equivalent to CHAR_MIN, SHRT_MIN,FLT_MIN, DBL_MIN, etc.
Equivalent to CHAR_MAX, SHRT_MAX,FLT_MAX, DBL_MAX, etc.
lowest() is necessary because not all floating-point representations have a smallest (most negative) value that is the negative of the largest (most positive) finite value.
Equivalent to FLT_MANT_DIG, DBL_MANT_DIG,LDBL_MANT_DIG.
Equivalent to FLT_DIG, DBL_DIG,LDBL_DIG.
Equivalent to FLT_RADIX.
Distinguishes types with bases other than 2 (e.g., BCD).
Equivalent to FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON.
Rounding error is described in ISO/IEC 10967-1:2012 Section 5.2.4 and Annex C Rationale Section C.5.2.4 â Rounding and rounding constants.
Equivalent to FLT_MIN_EXP, DBL_MIN_EXP,LDBL_MIN_EXP.
Equivalent toFLT_MIN_10_EXP, DBL_MIN_10_EXP, LDBL_MIN_10_EXP.
Equivalent to FLT_MAX_EXP,DBL_MAX_EXP, LDBL_MAX_EXP.
Equivalent toFLT_MAX_10_EXP, DBL_MAX_10_EXP, LDBL_MAX_10_EXP.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
ISO/IEC 60559:2020 is the same as IEEE 754-2019.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
Required by ISO/IEC 10967-1:2012.
Refer to ISO/IEC 60559.
Required by ISO/IEC 10967-1:2012.
Equivalent to FLT_ROUNDS.
Required by ISO/IEC 10967-1:2012.
17.3.5.3 numeric_limits specializations [numeric.special]
All members shall be provided for all specializations.
However, many values are only required to be meaningful under certain conditions (for example,epsilon() is only meaningful ifis_integer isfalse).
Any value that is not âmeaningfulâ shall be set to 0 orfalse.
[Example 1: namespace std {template<> class numeric_limits {public:static constexpr bool is_specialized = true; static constexpr float min() noexcept { return 1.17549435E-38F; }static constexpr float max() noexcept { return 3.40282347E+38F; }static constexpr float lowest() noexcept { return -3.40282347E+38F; }static constexpr int digits = 24; static constexpr int digits10 = 6; static constexpr int max_digits10 = 9; static constexpr bool is_signed = true; static constexpr bool is_integer = false; static constexpr bool is_exact = false; static constexpr int radix = 2; static constexpr float epsilon() noexcept { return 1.19209290E-07F; }static constexpr float round_error() noexcept { return 0.5F; }static constexpr int min_exponent = -125; static constexpr int min_exponent10 = - 37; static constexpr int max_exponent = +128; static constexpr int max_exponent10 = + 38; static constexpr bool has_infinity = true; static constexpr bool has_quiet_NaN = true; static constexpr bool has_signaling_NaN = true; static constexpr float infinity() noexcept { return value; }static constexpr float quiet_NaN() noexcept { return value; }static constexpr float signaling_NaN() noexcept { return value; }static constexpr float denorm_min() noexcept { return min(); }static constexpr bool is_iec559 = true; static constexpr bool is_bounded = true; static constexpr bool is_modulo = false; static constexpr bool traps = true; static constexpr bool tinyness_before = true; static constexpr float_round_style round_style = round_to_nearest; };} â end example]
The specialization forbool shall be provided as follows:
namespace std {template<> class numeric_limits {public:static constexpr bool is_specialized = true; static constexpr bool min() noexcept { return false; }static constexpr bool max() noexcept { return true; }static constexpr bool lowest() noexcept { return false; }static constexpr int digits = 1; static constexpr int digits10 = 0; static constexpr int max_digits10 = 0; static constexpr bool is_signed = false; static constexpr bool is_integer = true; static constexpr bool is_exact = true; static constexpr int radix = 2; static constexpr bool epsilon() noexcept { return 0; }static constexpr bool round_error() noexcept { return 0; }static constexpr int min_exponent = 0; static constexpr int min_exponent10 = 0; static constexpr int max_exponent = 0; static constexpr int max_exponent10 = 0; static constexpr bool has_infinity = false; static constexpr bool has_quiet_NaN = false; static constexpr bool has_signaling_NaN = false; static constexpr bool infinity() noexcept { return 0; }static constexpr bool quiet_NaN() noexcept { return 0; }static constexpr bool signaling_NaN() noexcept { return 0; }static constexpr bool denorm_min() noexcept { return 0; }static constexpr bool is_iec559 = false; static constexpr bool is_bounded = true; static constexpr bool is_modulo = false; static constexpr bool traps = false; static constexpr bool tinyness_before = false; static constexpr float_round_style round_style = round_toward_zero; };}
17.3.6 Header synopsis [climits.syn]
// all freestanding#define BOOL_WIDTH see below#define CHAR_BIT see below#define CHAR_WIDTH see below#define SCHAR_WIDTH see below#define UCHAR_WIDTH see below#define USHRT_WIDTH see below#define SHRT_WIDTH see below#define UINT_WIDTH see below#define INT_WIDTH see below#define ULONG_WIDTH see below#define LONG_WIDTH see below#define ULLONG_WIDTH see below#define LLONG_WIDTH see below#define SCHAR_MIN see below#define SCHAR_MAX see below#define UCHAR_MAX see below#define CHAR_MIN see below#define CHAR_MAX see below#define MB_LEN_MAX see below#define SHRT_MIN see below#define SHRT_MAX see below#define USHRT_MAX see below#define INT_MIN see below#define INT_MAX see below#define UINT_MAX see below#define LONG_MIN see below#define LONG_MAX see below#define ULONG_MAX see below#define LLONG_MIN see below#define LLONG_MAX see below#define ULLONG_MAX see below
The header defines all macros the same as the C standard library header <limits.h>, except that it does not define the macro BITINT_MAXWIDTH.
[Note 1:
Except for the WIDTH macros, CHAR_BIT, and MB_LEN_MAX, a macro referring to an integer type T defines a constant whose type is the promoted type of T ([conv.prom]).
â end note]
See also: ISO/IEC 9899:2024, 5.2.4.2.1
17.3.7 Header synopsis [cfloat.syn]
// all freestanding#define STDC_VERSION_FLOAT_H 202311L#define FLT_ROUNDS see below#define FLT_EVAL_METHOD see below#define FLT_RADIX see below#define INFINITY see below#define NAN see below#define FLT_SNAN see below#define DBL_SNAN see below#define LDBL_SNAN see below#define FLT_MANT_DIG see below#define DBL_MANT_DIG see below#define LDBL_MANT_DIG see below#define FLT_DECIMAL_DIG see below#define DBL_DECIMAL_DIG see below#define LDBL_DECIMAL_DIG see below#define FLT_DIG see below#define DBL_DIG see below#define LDBL_DIG see below#define FLT_MIN_EXP see below#define DBL_MIN_EXP see below#define LDBL_MIN_EXP see below#define FLT_MIN_10_EXP see below#define DBL_MIN_10_EXP see below#define LDBL_MIN_10_EXP see below#define FLT_MAX_EXP see below#define DBL_MAX_EXP see below#define LDBL_MAX_EXP see below#define FLT_MAX_10_EXP see below#define DBL_MAX_10_EXP see below#define LDBL_MAX_10_EXP see below#define FLT_MAX see below#define DBL_MAX see below#define LDBL_MAX see below#define FLT_EPSILON see below#define DBL_EPSILON see below#define LDBL_EPSILON see below#define FLT_MIN see below#define DBL_MIN see below#define LDBL_MIN see below#define FLT_TRUE_MIN see below#define DBL_TRUE_MIN see below#define LDBL_TRUE_MIN see below
The header defines all macros the same as the C standard library header <float.h>.
See also: ISO/IEC 9899:2024, 5.2.4.2.2