26 Numerics library [numerics]

26.5 Bit manipulation [bit]

26.5.6 Counting [bit.count]

In the following descriptions, let N denote numeric_­limits<T>​::​digits.
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template<class T> constexpr int countl_zero(T x) noexcept;
1
#
Constraints: T is an unsigned integer type ([basic.fundamental]).
2
#
Returns: The number of consecutive 0 bits in the value of x, starting from the most significant bit.
[ Note
:
Returns N if x == 0.
— end note
 ]
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template<class T> constexpr int countl_one(T x) noexcept;
3
#
Constraints: T is an unsigned integer type ([basic.fundamental]).
4
#
Returns: The number of consecutive 1 bits in the value of x, starting from the most significant bit.
[ Note
:
Returns N if x == numeric_­limits<T>​::​max().
— end note
 ]
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template<class T> constexpr int countr_zero(T x) noexcept;
5
#
Constraints: T is an unsigned integer type ([basic.fundamental]).
6
#
Returns: The number of consecutive 0 bits in the value of x, starting from the least significant bit.
[ Note
:
Returns N if x == 0.
— end note
 ]
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template<class T> constexpr int countr_one(T x) noexcept;
7
#
Constraints: T is an unsigned integer type ([basic.fundamental]).
8
#
Returns: The number of consecutive 1 bits in the value of x, starting from the least significant bit.
[ Note
:
Returns N if x == numeric_­limits<T>​::​max().
— end note
 ]
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template<class T> constexpr int popcount(T x) noexcept;
9
#
Constraints: T is an unsigned integer type ([basic.fundamental]).
10
#
Returns: The number of 1 bits in the value of x.