Standard library header <cfloat>

C++

Language

Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Standard Library header files

Language Support
<cstddef> <limits> <climits> <contract>	<cfloat> <cstdint> <new> <version>	<typeinfo> <exception> <initializer_list>	<csignal> <csetjmp> <cstdarg>
Concepts
<concepts>
Diagnostics
<stdexcept>	<cassert>	<cerrno>	<system_error>
General utilities
<utility> <memory> <memory_resource> <scoped_allocator> <compare>	<bitset> <tuple> <optional> <any> <variant>	<type_traits> <ratio> <chrono> <typeindex> <functional>	<ctime> <cstdlib>
Strings
<string> <string_view>	<cctype> <cwctype>	<cwchar> <cuchar>	<cstring> <charconv>
Localization
<locale>	<codecvt>	<clocale>
Containers
<span> <array> <vector>	<deque> <forward_list> <list>	<map> <set> <queue>	<unordered_map> <unordered_set> <stack>
Iterators
<iterator>
Algorithms
<algorithm>	<execution>
Numerics
<complex> <random>	<valarray> <numeric>	<cfenv> <cmath>	<bit>
Input/Output
<iosfwd> <ios> <iomanip> <streambuf>	<istream> <ostream> <iostream>	<sstream> <fstream> <syncstream>	<cstdio> <cinttypes> <strstream>
Regular expressions
<regex>
Filesystem support
<filesystem>
Thread support
<thread> <atomic>	<mutex> <shared_mutex>	<condition_variable> <future>
C compatibility
<ciso646> <cstdalign>	<cstdbool> <ccomplex>	<ctgmath>

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

This header is part of the type support library, in particular it's 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 long double to decimal with at least DECIMAL_DIG digits and back to long double is the identity conversion.: this is the decimal precision required to serialize/deserialize a long double (see also std::numeric_limits::max_digits10) (macro constant)
FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG (C++17)	conversion from float/double/long double 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 long double respectively (macro constant)
FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN (C++17)	minimum positive value of float, double and long double respectively (macro constant)
FLT_MAXDBL_MAXLDBL_MAX	maximum value of float, double and long double respectively (macro constant)
FLT_EPSILONDBL_EPSILONLDBL_EPSILON	difference between 1.0 and the next representable value for float, double and long double respectively (macro constant)
FLT_DIGDBL_DIGLDBL_DIG	number of decimal digits that are guaranteed to be preserved in text -> float/double/long double -> 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 long double 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 long double respectively (macro constant)
FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP	minimum negative integer such that 10 raised by power one less than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP	maximum positive integer such that FLT_RADIX raised by power one more than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP	maximum positive integer such that 10 raised by power one more than that integer is a normalized float, double and long double respectively (macro constant)
FLT_ROUNDS	default rounding mode of floating-point arithmetics (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*/