Source code
Revision control
Copy as Markdown
Other Tools
use core::num::Wrapping;
use core::ops::Neg;
use crate::float::FloatCore;
use crate::Num;
/// Useful functions for signed numbers (i.e. numbers that can be negative).
pub trait Signed: Sized + Num + Neg<Output = Self> {
/// Computes the absolute value.
///
/// For `f32` and `f64`, `NaN` will be returned if the number is `NaN`.
///
/// For signed integers, `::MIN` will be returned if the number is `::MIN`.
fn abs(&self) -> Self;
/// The positive difference of two numbers.
///
/// Returns `zero` if the number is less than or equal to `other`, otherwise the difference
/// between `self` and `other` is returned.
fn abs_sub(&self, other: &Self) -> Self;
/// Returns the sign of the number.
///
/// For `f32` and `f64`:
///
/// * `1.0` if the number is positive, `+0.0` or `INFINITY`
/// * `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
/// * `NaN` if the number is `NaN`
///
/// For signed integers:
///
/// * `0` if the number is zero
/// * `1` if the number is positive
/// * `-1` if the number is negative
fn signum(&self) -> Self;
/// Returns true if the number is positive and false if the number is zero or negative.
fn is_positive(&self) -> bool;
/// Returns true if the number is negative and false if the number is zero or positive.
fn is_negative(&self) -> bool;
}
macro_rules! signed_impl {
($($t:ty)*) => ($(
impl Signed for $t {
#[inline]
fn abs(&self) -> $t {
if self.is_negative() { -*self } else { *self }
}
#[inline]
fn abs_sub(&self, other: &$t) -> $t {
if *self <= *other { 0 } else { *self - *other }
}
#[inline]
fn signum(&self) -> $t {
match *self {
n if n > 0 => 1,
0 => 0,
_ => -1,
}
}
#[inline]
fn is_positive(&self) -> bool { *self > 0 }
#[inline]
fn is_negative(&self) -> bool { *self < 0 }
}
)*)
}
signed_impl!(isize i8 i16 i32 i64 i128);
impl<T: Signed> Signed for Wrapping<T>
where
Wrapping<T>: Num + Neg<Output = Wrapping<T>>,
{
#[inline]
fn abs(&self) -> Self {
Wrapping(self.0.abs())
}
#[inline]
fn abs_sub(&self, other: &Self) -> Self {
Wrapping(self.0.abs_sub(&other.0))
}
#[inline]
fn signum(&self) -> Self {
Wrapping(self.0.signum())
}
#[inline]
fn is_positive(&self) -> bool {
self.0.is_positive()
}
#[inline]
fn is_negative(&self) -> bool {
self.0.is_negative()
}
}
macro_rules! signed_float_impl {
($t:ty) => {
impl Signed for $t {
/// Computes the absolute value. Returns `NAN` if the number is `NAN`.
#[inline]
fn abs(&self) -> $t {
FloatCore::abs(*self)
}
/// The positive difference of two numbers. Returns `0.0` if the number is
/// less than or equal to `other`, otherwise the difference between`self`
/// and `other` is returned.
#[inline]
fn abs_sub(&self, other: &$t) -> $t {
if *self <= *other {
0.
} else {
*self - *other
}
}
/// # Returns
///
/// - `1.0` if the number is positive, `+0.0` or `INFINITY`
/// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
/// - `NAN` if the number is NaN
#[inline]
fn signum(&self) -> $t {
FloatCore::signum(*self)
}
/// Returns `true` if the number is positive, including `+0.0` and `INFINITY`
#[inline]
fn is_positive(&self) -> bool {
FloatCore::is_sign_positive(*self)
}
/// Returns `true` if the number is negative, including `-0.0` and `NEG_INFINITY`
#[inline]
fn is_negative(&self) -> bool {
FloatCore::is_sign_negative(*self)
}
}
};
}
signed_float_impl!(f32);
signed_float_impl!(f64);
/// Computes the absolute value.
///
/// For `f32` and `f64`, `NaN` will be returned if the number is `NaN`
///
/// For signed integers, `::MIN` will be returned if the number is `::MIN`.
#[inline(always)]
pub fn abs<T: Signed>(value: T) -> T {
value.abs()
}
/// The positive difference of two numbers.
///
/// Returns zero if `x` is less than or equal to `y`, otherwise the difference
/// between `x` and `y` is returned.
#[inline(always)]
pub fn abs_sub<T: Signed>(x: T, y: T) -> T {
x.abs_sub(&y)
}
/// Returns the sign of the number.
///
/// For `f32` and `f64`:
///
/// * `1.0` if the number is positive, `+0.0` or `INFINITY`
/// * `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
/// * `NaN` if the number is `NaN`
///
/// For signed integers:
///
/// * `0` if the number is zero
/// * `1` if the number is positive
/// * `-1` if the number is negative
#[inline(always)]
pub fn signum<T: Signed>(value: T) -> T {
value.signum()
}
/// A trait for values which cannot be negative
pub trait Unsigned: Num {}
macro_rules! empty_trait_impl {
($name:ident for $($t:ty)*) => ($(
impl $name for $t {}
)*)
}
empty_trait_impl!(Unsigned for usize u8 u16 u32 u64 u128);
impl<T: Unsigned> Unsigned for Wrapping<T> where Wrapping<T>: Num {}
#[test]
fn unsigned_wrapping_is_unsigned() {
fn require_unsigned<T: Unsigned>(_: &T) {}
require_unsigned(&Wrapping(42_u32));
}
#[test]
fn signed_wrapping_is_signed() {
fn require_signed<T: Signed>(_: &T) {}
require_signed(&Wrapping(-42));
}