std::numeric_limits<T>::digits10
From cppreference.com
< cpp | types | numeric limits
static const int digits10; |
(until C++11) | |
| static constexpr int digits10; |
(since C++11) | |
The value of std::numeric_limits<T>::digits10 is the number of base-10 digits that can be represented by the type T without change, that is, any number with this many significant decimal digits can be converted to a value of type T and back to decimal form, without change due to rounding or overflow. For base-radix types, it is the value of digits() (digits - 1 for floating-point types) multiplied by log10(radix) and rounded down.
[edit] Standard specializations
T
|
value of std::numeric_limits<T>::digits10 |
| /* non-specialized */ | 0 |
| bool | 0 |
| char | std::numeric_limits<char>::digits * std::log10(2) |
| signed char | std::numeric_limits<signed char>::digits * std::log10(2) |
| unsigned char | std::numeric_limits<unsigned char>::digits * std::log10(2) |
| wchar_t | std::numeric_limits<wchar_t>::digits * |