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//! Traits for abstracting over Boolean types.
//!
//! These traits are mainly useful for allowing SIMD values, where bit masks are
//! typically used instead of `bool`.
use core::ops::{BitAnd, BitOr, BitXor, Not};
#[cfg(feature = "wide")]
mod wide;
/// Associates a Boolean type to the implementing type.
///
/// This is primarily used in traits and functions that can accept SIMD values
/// and return a Boolean result. SIMD values use masks to select different values for
/// each lane and `HasBoolMask::Mask` can be used to know which type that mask
/// has.
pub trait HasBoolMask {
/// The mask type to use for selecting `Self` values.
type Mask: BoolMask;
}
impl<T> HasBoolMask for &'_ T
where
T: HasBoolMask,
{
type Mask = T::Mask;
}
impl<T> HasBoolMask for &'_ mut T
where
T: HasBoolMask,
{
type Mask = T::Mask;
}
impl<T> HasBoolMask for [T]
where
T: HasBoolMask,
{
type Mask = T::Mask;
}
impl<T, const N: usize> HasBoolMask for [T; N]
where
T: HasBoolMask,
{
type Mask = T::Mask;
}
macro_rules! impl_has_bool_mask {
($($ty:ident),+) => {
$(
impl HasBoolMask for $ty {
type Mask = bool;
}
)+
};
}
impl_has_bool_mask!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, f32, f64);
/// Basic methods for boolean masks.
pub trait BoolMask {
/// Create a new mask where each lane is set to `value`.
#[must_use]
fn from_bool(value: bool) -> Self;
/// Checks if all lanes in the mask are `true`.
#[must_use]
fn is_true(&self) -> bool;
/// Checks if all lanes in the mask are `false`.
#[must_use]
fn is_false(&self) -> bool;
}
impl BoolMask for bool {
#[inline]
fn from_bool(value: bool) -> Self {
value
}
#[inline]
fn is_true(&self) -> bool {
*self
}
#[inline]
fn is_false(&self) -> bool {
!*self
}
}
/// Makes a mask bale to select between two values.
pub trait Select<T>
where
T: HasBoolMask<Mask = Self>,
{
/// Select lanes from `a` when corresponding lanes in `self` are `true`, and
/// select from `b` when `false`.
#[must_use]
fn select(self, a: T, b: T) -> T;
}
impl<T> Select<T> for bool
where
T: HasBoolMask<Mask = Self>,
{
#[inline(always)]
fn select(self, a: T, b: T) -> T {
if self {
a
} else {
b
}
}
}
/// Like [`Select`], but can avoid evaluating the input.
pub trait LazySelect<T>: Select<T>
where
T: HasBoolMask<Mask = Self>,
{
/// Select lanes from the output of `a` when corresponding lanes in `self`
/// are `true`, and select from the output of `b` when `false`. May avoid
/// evaluating either option if it's not selected.
#[must_use]
fn lazy_select<A, B>(self, a: A, b: B) -> T
where
A: FnOnce() -> T,
B: FnOnce() -> T;
}
impl<T> LazySelect<T> for bool
where
T: HasBoolMask<Mask = Self>,
{
#[inline(always)]
fn lazy_select<A, B>(self, a: A, b: B) -> T
where
A: FnOnce() -> T,
B: FnOnce() -> T,
{
if self {
a()
} else {
b()
}
}
}
/// A helper trait that collects bit traits under one name.
pub trait BitOps:
Sized
+ BitAnd<Output = Self>
+ BitOr<Output = Self>
+ BitXor<Output = Self>
+ Not<Output = Self>
+ for<'a> BitAnd<&'a Self, Output = Self>
+ for<'a> BitOr<&'a Self, Output = Self>
+ for<'a> BitXor<&'a Self, Output = Self>
{
}
impl<T> BitOps for T where
T: Sized
+ BitAnd<Output = Self>
+ BitOr<Output = Self>
+ BitXor<Output = Self>
+ Not<Output = Self>
+ for<'a> BitAnd<&'a Self, Output = Self>
+ for<'a> BitOr<&'a Self, Output = Self>
+ for<'a> BitXor<&'a Self, Output = Self>
{
}