static constexpr int max_digits10 | (since C++11) |
The value of std::numeric_limits<T>::max_digits10 is the number of base-10 digits that are necessary to uniquely represent all distinct values of the type T, such as necessary for serialization/deserialization to text. This constant is meaningful for all floating-point types.
Standard specializations
T | value of std::numeric_limits<T>::max_digits10 |
|---|---|
| /* non-specialized */ | 0 |
bool | 0 |
char | 0 |
signed char | 0 |
unsigned char | 0 |
wchar_t | 0 |
char16_t | 0 |
char32_t | 0 |
short | 0 |
unsigned short | 0 |
int | 0 |
unsigned int | 0 |
long | 0 |
unsigned long | 0 |
long long | 0 |
unsigned long long | 0 |
float | std::floor(std::numeric_limits<float>::digits * std::log10(2) + 2) |
double | std::floor(std::numeric_limits<double>::digits * std::log10(2) + 2) |
long double | std::floor(std::numeric_limits<long double>::digits * std::log10(2) + 2) |
Notes
Unlike most mathematical operations, the conversion of a floating-point value to text and back is exact as long as at least max_digits10 were used (9 for float, 17 for double): it is guaranteed to produce the same floating-point value, even though the intermediate text representation is not exact. It may take over a hundred decimal digits to represent the precise value of a float in decimal notation.
See also
| [static] | the radix or integer base used by the representation of the given type (public static member constant) |
| [static] | number of radix digits that can be represented without change (public static member constant) |
| [static] | number of decimal digits that can be represented without change (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) |
Please login to continue.