std::numeric_limits::digits

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std::numeric_limits
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numeric_limits::digits
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static const int digits;
 (until C++11)
static constexpr int digits;
 (since C++11)

The value of std::numeric_limits<T>::digits is the number of digits in base-radix that can be represented by the type T without change. For integer types, this is the number of bits not counting the sign bit and the padding bits (if any). For floating-point types, this is the number of digits in the mantissa.

Standard specializations

T value of std::numeric_limits<T>::digits (assuming no padding bits)
/* non-specialized */ ​0​
bool 1
char CHAR_BIT - std::numeric_limits<char>::is_signed
signed char CHAR_BIT - 1
unsigned char CHAR_BIT
wchar_t CHAR_BIT*sizeof(wchar_t) - std::numeric_limits<wchar_t>::is_signed
char8_t CHAR_BIT
char16_t CHAR_BIT*sizeof(char16_t)
char32_t CHAR_BIT*sizeof(char32_t)
short CHAR_BIT*sizeof(short)-1
unsigned short CHAR_BIT*sizeof(short)
int CHAR_BIT*sizeof(int)-1
unsigned int CHAR_BIT*sizeof(int)
long CHAR_BIT*sizeof(long)-1
unsigned long CHAR_BIT*sizeof(long)
long long CHAR_BIT*sizeof(long long)-1
unsigned long long CHAR_BIT*sizeof(long long)
float FLT_MANT_DIG
double DBL_MANT_DIG
long double LDBL_MANT_DIG

See also

[static]
 the radix or integer base used by the representation of the given type
(public static member constant)
[static]
 one more than the smallest negative power of the radix that is a valid normalized floating-point value
(public static member constant)
[static]
 one more than the largest integer power of the radix that is a valid finite floating-point value
(public static member constant)
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