Standard library header <cfloat>

 

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Standard library headers

Language support <cfloat> <climits> <compare>(C++20) <contracts>(C++26) <coroutine>(C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint>(C++11) <cstdlib> <exception> <initializer_list>(C++11)    <limits> <new> <source_location>(C++20) <stdfloat>(C++23) <typeinfo> <version>(C++20) Concepts <concepts>(C++20) Diagnostics <cassert> <cerrno> <debugging>(C++26) <stacktrace>(C++23) <stdexcept> <system_error>(C++11) Memory management <memory> <memory_resource>(C++17) <scoped_allocator>(C++11) Metaprogramming <type_traits>(C++11) <ratio>(C++11)

General utilities <any>(C++17) <bitset> <bit>(C++20) <charconv>(C++17) <expected>(C++23) <format>(C++20) <functional> <optional>(C++17) <stdbit.h>(C++26) <tuple>(C++11) <typeindex>(C++11) <utility> <variant>(C++17) Containers <array>(C++11) <deque> <flat_map>(C++23) <flat_set>(C++23) <forward_list>(C++11) <hive>(C++26) <inplace_vector>(C++26)    <list> <map> <mdspan>(C++23) <queue> <set> <span>(C++20) <stack> <unordered_map>(C++11) <unordered_set>(C++11) <vector> Iterators <iterator> Ranges <generator>(C++23) <ranges>(C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar>(C++11) <cwchar> <cwctype> <string_view>(C++17) <string> Text processing <clocale> <codecvt>(C++11/17/26*) <locale> <regex>(C++11) <text_encoding>(C++26)    Numerics <cfenv>(C++11) <cmath> <complex> <linalg>(C++26) <numbers>(C++20) <random>(C++11) <simd>(C++26) <stdckdint.h>(C++26) <valarray> Time <chrono>(C++11) <ctime> C compatibility <ccomplex>(C++11/17/20*) <ciso646>(until C++20) <cstdalign>(C++11/17/20*) <cstdbool>(C++11/17/20*) <ctgmath>(C++11/17/20*)

Input/output <cinttypes>(C++11) <cstdio> <filesystem>(C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print>(C++23) <spanstream>(C++23) <sstream> <streambuf> <strstream>(C++98/26*) <syncstream>(C++20) Concurrency support <atomic>(C++11) <barrier>(C++20) <condition_variable>(C++11) <future>(C++11) <hazard_pointer>(C++26) <latch>(C++20) <mutex>(C++11) <rcu>(C++26) <semaphore>(C++20) <shared_mutex>(C++14) <stdatomic.h>(C++23) <stop_token>(C++20) <thread>(C++11) Execution support <execution>(C++17)

 

This header was originally in the C standard library as <float.h>.

This header is part of the type support library, in particular, it is a part of the C numeric limits interface.

Macros

FLT_RADIX	the radix (integer base) used by the representation of all three floating-point types (macro constant)
DECIMAL_DIG (C++11)	conversion from longdouble to decimal with at least DECIMAL_DIG digits and back to longdouble is the identity conversion: this is the decimal precision required to serialize/deserialize a longdouble (see also std::numeric_limits::max_digits10) (macro constant)
FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG (C++17)	conversion from float/double/longdouble to decimal with at least FLT_DECIMAL_DIG/DBL_DECIMAL_DIG/LDBL_DECIMAL_DIG digits and back is the identity conversion: this is the decimal precision required to serialize/deserialize a floating-point value (see also std::numeric_limits::max_digits10). Defined to at least 6, 10, and 10 respectively, or 9 for IEEE float and 17 for IEEE double. (macro constant)
FLT_MINDBL_MINLDBL_MIN	minimum normalized positive value of float, double and longdouble respectively (macro constant)
FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN (C++17)	minimum positive value of float, double and longdouble respectively (macro constant)
FLT_MAXDBL_MAXLDBL_MAX	maximum finite value of float, double and longdouble respectively (macro constant)
FLT_EPSILONDBL_EPSILONLDBL_EPSILON	difference between 1.0 and the next representable value for float, double and longdouble respectively (macro constant)
FLT_DIGDBL_DIGLDBL_DIG	number of decimal digits that are guaranteed to be preserved in text → float/double/longdouble → text roundtrip without change due to rounding or overflow (see std::numeric_limits::digits10 for explanation) (macro constant)
FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG	number of base FLT_RADIX digits that can be represented without losing precision for float, double and longdouble respectively (macro constant)
FLT_MIN_EXPDBL_MIN_EXPLDBL_MIN_EXP	minimum negative integer such that FLT_RADIX raised by power one less than that integer is a normalized float, double and longdouble respectively (macro constant)
FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP	minimum negative integer such that 10 raised to that power is a normalized float, double and longdouble respectively (macro constant)
FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP	maximum positive integer such that FLT_RADIX raised by power one less than that integer is a representable finite float, double and longdouble respectively (macro constant)
FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP	maximum positive integer such that 10 raised to that power is a representable finite float, double and longdouble respectively (macro constant)
FLT_ROUNDS	default rounding mode of floating-point arithmetic (macro constant)
FLT_EVAL_METHOD (C++11)	specifies in what precision all arithmetic operations are done (macro constant)
FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM (C++17)	specifies whether the type supports subnormal (denormal) numbers: -1 – indeterminable, ​0​ – absent, 1 – present (macro constant)

Synopsis

#define FLT_ROUNDS /* see definition */#define FLT_EVAL_METHOD /* see definition */#define FLT_HAS_SUBNORM /* see definition */#define DBL_HAS_SUBNORM /* see definition */#define LDBL_HAS_SUBNORM /* see definition */#define FLT_RADIX /* see definition */#define FLT_MANT_DIG /* see definition */#define DBL_MANT_DIG /* see definition */#define LDBL_MANT_DIG /* see definition */#define FLT_DECIMAL_DIG /* see definition */#define DBL_DECIMAL_DIG /* see definition */#define LDBL_DECIMAL_DIG /* see definition */#define DECIMAL_DIG /* see definition */#define FLT_DIG /* see definition */#define DBL_DIG /* see definition */#define LDBL_DIG /* see definition */#define FLT_MIN_EXP /* see definition */#define DBL_MIN_EXP /* see definition */#define LDBL_MIN_EXP /* see definition */#define FLT_MIN_10_EXP /* see definition */#define DBL_MIN_10_EXP /* see definition */#define LDBL_MIN_10_EXP /* see definition */#define FLT_MAX_EXP /* see definition */#define DBL_MAX_EXP /* see definition */#define LDBL_MAX_EXP /* see definition */#define FLT_MAX_10_EXP /* see definition */#define DBL_MAX_10_EXP /* see definition */#define LDBL_MAX_10_EXP /* see definition */#define FLT_MAX /* see definition */#define DBL_MAX /* see definition */#define LDBL_MAX /* see definition */#define FLT_EPSILON /* see definition */#define DBL_EPSILON /* see definition */#define LDBL_EPSILON /* see definition */#define FLT_MIN /* see definition */#define DBL_MIN /* see definition */#define LDBL_MIN /* see definition */#define FLT_TRUE_MIN /* see definition */#define DBL_TRUE_MIN /* see definition */#define LDBL_TRUE_MIN /* see definition */

See also

C documentation for Limits of floating-point types