Standard library header <cfloat>

 

C++

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Concepts library (C++20)

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External libraries

 

Standard library headers

Language support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11) <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (C++20)
Diagnostics
<stdexcept> <stacktrace> (C++23)	<cassert>	<cerrno>	<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
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
Strings
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
Containers
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23)
Iterators
<iterator>
Ranges
<ranges> (C++20)	<generator> (C++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath>	<numbers> (C++20)
Time
<chrono> (C++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (C++11/17*)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11)
C compatibility
<cstdbool> (C++11/17/20*)   <ccomplex> (C++11/17/20*)	<ctgmath> (C++11/17/20*)	<cstdalign> (C++11/17/20*)	<ciso646> (until C++20)

 

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 finite 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 to that power 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 less than that integer is a representable finite 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 to that power is a representable finite float, double and long double 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 */