Defined in header
template< class T >
constexpr int bit_width( T x ) noexcept;
If x is not zero, calculates the number of bits needed to store the value x, that is, 1 + floor(log
2(x)). If x is zero, returns zero.
This overload participates in overload resolution only if
T is an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type).
|x||-||unsigned integer value|
 Return value
Zero if x is zero; otherwise, one plus the base-2 logarithm of x, with any fractional part discarded.
||202002L||(C++20)||Integral power-of-2 operations|
bit_width( 0000 ) = 0 bit_width( 0001 ) = 1 bit_width( 0010 ) = 2 bit_width( 0011 ) = 2 bit_width( 0100 ) = 3 bit_width( 0101 ) = 3 bit_width( 0110 ) = 3 bit_width( 0111 ) = 3
 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 3656||C++20||the return type of
||made it int|
 See also
| counts the number of consecutive 0 bits, starting from the most significant bit |