See also std::numeric_limits interface.
[edit] Limits of integer types Limits of core language integer types bit width of byteSCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN
(C++11)
minimum value of signed char, short, int, long and long long respectivelySCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX
(C++11)
maximum value of signed char, short, int, long and long long respectivelyUCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX
(C++11)
maximum value of unsigned char, unsigned short, unsigned int,std::wint_t
std::wint_t
The types of these constants, other than CHAR_BIT and MB_LEN_MAX, are required to match the results of the integral promotions as applied to objects of the types they describe: CHAR_MAX may have type int or unsigned int, but never char. Similarly USHRT_MAX may not be of an unsigned type: its type may be int.
A freestanding implementation may lack std::sig_atomic_t and/or std::wint_t typedef names, in which case the SIG_ATOMIC_* and/or WINT_* macros are correspondingly absent.
#include <climits>
#include <cstdint>
#include <iomanip>
#include <iostream>
int main()
{
constexpr int 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 = 8 MB_LEN_MAX = 16 CHAR_MIN = -128 CHAR_MAX = 127 SCHAR_MIN = -128 SHRT_MIN = -32768 INT_MIN = -2147483648 LONG_MIN = -9223372036854775808 LLONG_MIN = -9223372036854775808 SCHAR_MAX = 127 SHRT_MAX = 32767 INT_MAX = 2147483647 LONG_MAX = 9223372036854775807 LLONG_MAX = 9223372036854775807 UCHAR_MAX = 255 USHRT_MAX = 65535 UINT_MAX = 4294967295 ULONG_MAX = 18446744073709551615 ULLONG_MAX = 18446744073709551615 PTRDIFF_MIN = -9223372036854775808 PTRDIFF_MAX = 9223372036854775807 SIZE_MAX = 18446744073709551615 SIG_ATOMIC_MIN = -2147483648 SIG_ATOMIC_MAX = 2147483647 WCHAR_MIN = -2147483648 WCHAR_MAX = 2147483647 WINT_MIN = 0 WINT_MAX = 4294967295[edit] Limits of floating-point types the radix (integer base) used by the representation of all three floating-point types
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.FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN
(C++17)
minimum positive value of float, double and long double respectivelyFLT_EPSILONDBL_EPSILONLDBL_EPSILON
difference between 1.0 and the next representable value for float, double and long double respectivelyFLT_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 respectivelyFLT_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 respectivelyFLT_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 respectivelyFLT_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 respectivelyFLT_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 respectivelyFLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM
(C++17)
specifies whether the type supports subnormal (denormal) numbers:#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 = 2 DECIMAL_DIG = 21 FLT_DECIMAL_DIG = 9 DBL_DECIMAL_DIG = 17 LDBL_DECIMAL_DIG = 21 FLT_MIN = 1.17549e-38 DBL_MIN = 2.22507e-308 LDBL_MIN = 3.3621e-4932 FLT_TRUE_MIN = 1.4013e-45 DBL_TRUE_MIN = 4.94066e-324 LDBL_TRUE_MIN = 3.6452e-4951 FLT_MAX = 3.40282e+38 DBL_MAX = 1.79769e+308 LDBL_MAX = 1.18973e+4932 FLT_EPSILON = 1.19209e-07 DBL_EPSILON = 2.22045e-16 LDBL_EPSILON = 1.0842e-19 FLT_DIG = 6 DBL_DIG = 15 LDBL_DIG = 18 FLT_MANT_DIG = 24 DBL_MANT_DIG = 53 LDBL_MANT_DIG = 64 FLT_MIN_EXP = -125 DBL_MIN_EXP = -1021 LDBL_MIN_EXP = -16381 FLT_MIN_10_EXP = -37 DBL_MIN_10_EXP = -307 LDBL_MIN_10_EXP = -4931 FLT_MAX_EXP = 128 DBL_MAX_EXP = 1024 LDBL_MAX_EXP = 16384 FLT_MAX_10_EXP = 38 DBL_MAX_10_EXP = 308 LDBL_MAX_10_EXP = 4932 FLT_ROUNDS = 1 FLT_EVAL_METHOD = 0 FLT_HAS_SUBNORM = 1 DBL_HAS_SUBNORM = 1 LDBL_HAS_SUBNORM = 1[edit] Defect reports
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 guaranteedRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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