|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Basic types | |||||||||||||||||||||
| Fixed width integer types(C++11) | |||||||||||||||||||||
| Fixed width floating-point types(C++23) | |||||||||||||||||||||
| |||||||||||||||||||||
| Numeric limits | |||||||||||||||||||||
| C numeric limits interface | |||||||||||||||||||||
| Runtime type information | |||||||||||||||||||||
| |||||||||||||||||||||
See alsostd::numeric_limits interface.
Contents |
Limits of core language integer types | |
Defined in header <climits> | |
CHAR_BIT | bit width of byte (macro constant)[edit] |
MB_LEN_MAX | maximum number of bytes in a multibyte character (macro constant)[edit] |
CHAR_MIN | minimum value ofchar (macro constant)[edit] |
CHAR_MAX | maximum value ofchar (macro constant)[edit] |
SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN (C++11) | minimum value ofsignedchar,short,int,long andlonglong respectively (macro constant)[edit] |
SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX (C++11) | maximum value ofsignedchar,short,int,long andlonglong respectively (macro constant)[edit] |
UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX (C++11) | maximum value ofunsignedchar,unsignedshort,unsignedint, unsignedlong andunsignedlonglong respectively (macro constant)[edit] |
Defined in header <cwchar> | |
Defined in header <cstdint> | |
WCHAR_MIN (C++11) | minimum value ofwchar_t (macro constant)[edit] |
WCHAR_MAX (C++11) | maximum value ofwchar_t (macro constant)[edit] |
Limits of library type aliases | |
Defined in header <cstdint> | |
PTRDIFF_MIN (C++11) | minimum value ofstd::ptrdiff_t (macro constant)[edit] |
PTRDIFF_MAX (C++11) | maximum value ofstd::ptrdiff_t (macro constant)[edit] |
SIZE_MAX (C++11) | maximum value ofstd::size_t (macro constant)[edit] |
SIG_ATOMIC_MIN (C++11) | minimum value ofstd::sig_atomic_t (macro constant)[edit] |
SIG_ATOMIC_MAX (C++11) | maximum value ofstd::sig_atomic_t (macro constant)[edit] |
WINT_MIN (C++11) | minimum value ofstd::wint_t(macro constant)[edit] |
WINT_MAX (C++11) | maximum value ofstd::wint_t(macro constant)[edit] |
The types of these constants, other thanCHAR_BIT andMB_LEN_MAX, are required to match the results of theintegral promotions as applied to objects of the types they describe:CHAR_MAX may have typeint orunsignedint, but neverchar. SimilarlyUSHRT_MAX may not be of an unsigned type: its type may beint.
Afreestanding implementation may lackstd::sig_atomic_t and/orstd::wint_t typedef names, in which case theSIG_ATOMIC_* and/orWINT_* macros are correspondingly absent.
#include <climits>#include <cstdint>#include <iomanip>#include <iostream> int main(){constexprint w=14;std::cout<<std::left;# define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n' COUT( CHAR_BIT); COUT( MB_LEN_MAX); COUT( CHAR_MIN); COUT( CHAR_MAX); COUT( SCHAR_MIN); COUT( SHRT_MIN); COUT( INT_MIN); COUT( LONG_MIN); COUT( LLONG_MIN); COUT( SCHAR_MAX); COUT( SHRT_MAX); COUT( INT_MAX); COUT( LONG_MAX); COUT( LLONG_MAX); COUT( UCHAR_MAX); COUT( USHRT_MAX); COUT( UINT_MAX); COUT( ULONG_MAX); COUT( ULLONG_MAX); COUT( PTRDIFF_MIN); COUT( PTRDIFF_MAX); COUT( SIZE_MAX); COUT( SIG_ATOMIC_MIN); COUT( SIG_ATOMIC_MAX); COUT( WCHAR_MIN); COUT( WCHAR_MAX); COUT( WINT_MIN); COUT( WINT_MAX);}
Possible output:
CHAR_BIT = 8MB_LEN_MAX = 16CHAR_MIN = -128CHAR_MAX = 127SCHAR_MIN = -128SHRT_MIN = -32768INT_MIN = -2147483648LONG_MIN = -9223372036854775808LLONG_MIN = -9223372036854775808SCHAR_MAX = 127SHRT_MAX = 32767INT_MAX = 2147483647LONG_MAX = 9223372036854775807LLONG_MAX = 9223372036854775807UCHAR_MAX = 255USHRT_MAX = 65535UINT_MAX = 4294967295ULONG_MAX = 18446744073709551615ULLONG_MAX = 18446744073709551615PTRDIFF_MIN = -9223372036854775808PTRDIFF_MAX = 9223372036854775807SIZE_MAX = 18446744073709551615SIG_ATOMIC_MIN = -2147483648SIG_ATOMIC_MAX = 2147483647WCHAR_MIN = -2147483648WCHAR_MAX = 2147483647WINT_MIN = 0WINT_MAX = 4294967295
Defined in header <cfloat> | |
FLT_RADIX | the radix (integer base) used by the representation of all three floating-point types (macro constant)[edit] |
DECIMAL_DIG (C++11) | conversion fromlongdouble to decimal with at leastDECIMAL_DIG digits and back tolongdouble is the identity conversion: this is the decimal precision required to serialize/deserialize alongdouble (see alsostd::numeric_limits::max_digits10) (macro constant)[edit] |
FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG (C++17) | conversion fromfloat/double/longdouble to decimal with at leastFLT_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 alsostd::numeric_limits::max_digits10). Defined to at least6,10, and10 respectively, or9 for IEEE float and17 for IEEE double. (macro constant)[edit] |
FLT_MINDBL_MINLDBL_MIN | minimum normalized positive value offloat,double andlongdouble respectively (macro constant)[edit] |
FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN (C++17) | minimum positive value offloat,double andlongdouble respectively (macro constant)[edit] |
FLT_MAXDBL_MAXLDBL_MAX | maximum finite value offloat,double andlongdouble respectively (macro constant)[edit] |
FLT_EPSILONDBL_EPSILONLDBL_EPSILON | difference between1.0 and the next representable value forfloat,double andlongdouble respectively (macro constant)[edit] |
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 (seestd::numeric_limits::digits10 for explanation) (macro constant)[edit] |
FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG | number of baseFLT_RADIX digits that can be represented without losing precision forfloat,double andlongdouble respectively (macro constant)[edit] |
FLT_MIN_EXPDBL_MIN_EXPLDBL_MIN_EXP | minimum negative integer such thatFLT_RADIX raised by power one less than that integer is a normalizedfloat,double andlongdouble respectively (macro constant)[edit] |
FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP | minimum negative integer such that10 raised to that power is a normalizedfloat,double andlongdouble respectively (macro constant)[edit] |
FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP | maximum positive integer such thatFLT_RADIX raised by power one less than that integer is a representable finitefloat,double andlongdouble respectively (macro constant)[edit] |
FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP | maximum positive integer such that10 raised to that power is a representable finitefloat,double andlongdouble respectively (macro constant)[edit] |
| default rounding mode of floating-point arithmetic (macro constant)[edit] | |
(C++11) | specifies in what precision all arithmetic operations are done (macro constant)[edit] |
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)[edit] |
#include <cfloat>#include <iomanip>#include <iostream> int main(){int w=16;std::cout<<std::left;// std::cout << std::setprecision(53);# define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n' COUT( FLT_RADIX); COUT( DECIMAL_DIG); COUT( FLT_DECIMAL_DIG); COUT( DBL_DECIMAL_DIG); COUT( LDBL_DECIMAL_DIG); COUT( FLT_MIN); COUT( DBL_MIN); COUT( LDBL_MIN); COUT( FLT_TRUE_MIN); COUT( DBL_TRUE_MIN); COUT( LDBL_TRUE_MIN); COUT( FLT_MAX); COUT( DBL_MAX); COUT( LDBL_MAX); COUT( FLT_EPSILON); COUT( DBL_EPSILON); COUT( LDBL_EPSILON); COUT( FLT_DIG); COUT( DBL_DIG); COUT( LDBL_DIG); COUT( FLT_MANT_DIG); COUT( DBL_MANT_DIG); COUT( LDBL_MANT_DIG); COUT( FLT_MIN_EXP); COUT( DBL_MIN_EXP); COUT( LDBL_MIN_EXP); COUT( FLT_MIN_10_EXP); COUT( DBL_MIN_10_EXP); COUT( LDBL_MIN_10_EXP); COUT( FLT_MAX_EXP); COUT( DBL_MAX_EXP); COUT( LDBL_MAX_EXP); COUT( FLT_MAX_10_EXP); COUT( DBL_MAX_10_EXP); COUT( LDBL_MAX_10_EXP); COUT(FLT_ROUNDS); COUT(FLT_EVAL_METHOD); COUT( FLT_HAS_SUBNORM); COUT( DBL_HAS_SUBNORM); COUT( LDBL_HAS_SUBNORM);}
Possible output:
FLT_RADIX = 2DECIMAL_DIG = 21FLT_DECIMAL_DIG = 9DBL_DECIMAL_DIG = 17LDBL_DECIMAL_DIG = 21FLT_MIN = 1.17549e-38DBL_MIN = 2.22507e-308LDBL_MIN = 3.3621e-4932FLT_TRUE_MIN = 1.4013e-45DBL_TRUE_MIN = 4.94066e-324LDBL_TRUE_MIN = 3.6452e-4951FLT_MAX = 3.40282e+38DBL_MAX = 1.79769e+308LDBL_MAX = 1.18973e+4932FLT_EPSILON = 1.19209e-07DBL_EPSILON = 2.22045e-16LDBL_EPSILON = 1.0842e-19FLT_DIG = 6DBL_DIG = 15LDBL_DIG = 18FLT_MANT_DIG = 24DBL_MANT_DIG = 53LDBL_MANT_DIG = 64FLT_MIN_EXP = -125DBL_MIN_EXP = -1021LDBL_MIN_EXP = -16381FLT_MIN_10_EXP = -37DBL_MIN_10_EXP = -307LDBL_MIN_10_EXP = -4931FLT_MAX_EXP = 128DBL_MAX_EXP = 1024LDBL_MAX_EXP = 16384FLT_MAX_10_EXP = 38DBL_MAX_10_EXP = 308LDBL_MAX_10_EXP = 4932FLT_ROUNDS = 1FLT_EVAL_METHOD = 0FLT_HAS_SUBNORM = 1DBL_HAS_SUBNORM = 1LDBL_HAS_SUBNORM = 1
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 416 | C++98 | it was unclear whether the types of the macros in<climits> are guaranteed to match the type to which they refer (C++ refers to C, and C says no) | clarified as not guaranteed |
C documentation forNumeric limits |
