Enum BitCount 

pub enum BitCount {
    Leading,
    Trailing,
    Ones,
    Parity,
    FirstSet,
}

Which question one of the bit counting builtins asks.

Three of these are an instruction on most machines and the other two are one of those and a little arithmetic, which is why they are one node with a question rather than five nodes.

Variants

Leading

__builtin_clz, the number of zero bits above the highest set one. Undefined for a zero argument, which is gcc’s rule and not an accident of any machine: bsr leaves its destination alone for a zero input rather than writing an answer to it.

Trailing

__builtin_ctz, the number of zero bits below the lowest set one. Undefined for a zero argument for the same reason.

Ones

__builtin_popcount, how many bits are set. Defined everywhere, including at zero.

Parity

__builtin_parity, whether the number of set bits is odd. Defined everywhere. Not the machine’s parity flag, which on x86-64 is over the low byte of the result and so answers a different question.

FirstSet

__builtin_ffs, the position of the lowest set bit counting from one, and zero for a zero argument. The one in the family that is defined at zero, and the one whose operand is signed, because that is the signature the C library’s ffs has.

Implementations

impl BitCount

pub const fn as_str(self) -> &'static str

How the question is written in the typed tree’s textual form.

Trait Implementations

impl Clone for BitCount

fn clone(&self) -> BitCount

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BitCount

impl Debug for BitCount

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for BitCount

impl PartialEq for BitCount

fn eq(&self, other: &BitCount) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BitCount