C numeric limits interface

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Utilities library

Language support Type support (basic types, RTTI) Library feature-test macros(C++20) Program utilities Variadic functions initializer_list (C++11) is_constant_evaluated (C++20) is_within_lifetime (C++26) source_location (C++20) Coroutine support(C++20) Contract support(C++26) Three-way comparison three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)   is_eqis_ltis_lteq (C++20)(C++20)(C++20)   is_neqis_gtis_gteq (C++20)(C++20)(C++20)

General utilities Function objects Bit manipulation(C++20) bitset hash (C++11) Relational operators(deprecated in C++20) rel_ops::operator!=rel_ops::operator>    rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)   cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23)

 

Type support

Basic types
Fixed width integer types(C++11)
Fixed width floating-point types(C++23)
ptrdiff_t size_t max_align_t (C++11)     byte (C++17)	nullptr_t (C++11) offsetof NULL
Numeric limits
numeric_limits
C numeric limits interface
Runtime type information
type_info type_index (C++11)	bad_typeid bad_cast

 

See also std::numeric_limits interface.

Limits of integer types

Limits of core language integer types
Defined in header <climits>
CHAR_BIT	bit width of byte (macro constant)
MB_LEN_MAX	maximum number of bytes in a multibyte character (macro constant)
CHAR_MIN	minimum value of char (macro constant)
CHAR_MAX	maximum value of char (macro constant)
SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN (C++11)	minimum value of signedchar, short, int, long and longlong respectively (macro constant)
SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX (C++11)	maximum value of signedchar, short, int, long and longlong respectively (macro constant)
UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX (C++11)	maximum value of unsignedchar, unsignedshort, unsignedint, unsignedlong and unsignedlonglong respectively (macro constant)
Defined in header <cwchar>
Defined in header <cstdint>
WCHAR_MIN (C++11)	minimum value of wchar_t (macro constant)
WCHAR_MAX (C++11)	maximum value of wchar_t (macro constant)
Limits of library type aliases
Defined in header <cstdint>
PTRDIFF_MIN (C++11)	minimum value of std::ptrdiff_t (macro constant)
PTRDIFF_MAX (C++11)	maximum value of std::ptrdiff_t (macro constant)
SIZE_MAX (C++11)	maximum value of std::size_t (macro constant)
SIG_ATOMIC_MIN (C++11)	minimum value of std::sig_atomic_t (macro constant)
SIG_ATOMIC_MAX (C++11)	maximum value of std::sig_atomic_t (macro constant)
WINT_MIN (C++11)	minimum value of std::wint_t (macro constant)
WINT_MAX (C++11)	maximum value of std::wint_t (macro constant)

Notes

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 unsignedint, 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.

Example

Run this code

#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 = 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

Limits of floating-point types

Defined in header <cfloat>
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)

Example

Run this code

#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

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 guaranteed to match the type to which they refer (C++ refers to C, and C says no)	clarified as not guaranteed

See also

• Fixed width integer types
• Arithmetic types
• C++ type system overview
• Type support (basic types, RTTI, type traits)

C documentation for Numeric limits