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Rollup merge of #102342 - jmillikin:nonzero-negation, r=scottmcm

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Add negation methods for signed non-zero integers.

Performing negation with defined wrapping semantics (such as `wrapping_neg()`) on a non-zero integer currently requires unpacking to a primitive and re-wrapping. Since negation of non-zero signed integers always produces a non-zero result, it is safe to implement the various `*_neg()` methods for `NonZeroI{N}`.

I'm not sure what to do about the `#[unstable(..., issue = "none")]` here -- should I file a tracking issue, or is that handled by the Rust dev team?

ACP: https://github.com/rust-lang/libs-team/issues/105
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Dylan DPC 2022-09-29 18:13:19 +05:30 committed by GitHub
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154
library/core/src/num/nonzero.rs
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@ -721,6 +721,160 @@ macro_rules! nonzero_signed_operations {
// SAFETY: absolute value of nonzero cannot yield zero values.
unsafe { $Uty::new_unchecked(self.get().unsigned_abs()) }
}
/// Returns `true` if `self` is negative and `false` if the
/// number is positive.
///
/// # Example
///
/// ```
/// #![feature(nonzero_negation_ops)]
///
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("let pos_five = ", stringify!($Ty), "::new(5)?;")]
#[doc = concat!("let neg_five = ", stringify!($Ty), "::new(-5)?;")]
///
/// assert!(neg_five.is_negative());
/// assert!(!pos_five.is_negative());
/// # Some(())
/// # }
/// ```
#[must_use]
#[inline]
#[unstable(feature = "nonzero_negation_ops", issue = "102443")]
pub const fn is_negative(self) -> bool {
self.get().is_negative()
}
/// Checked negation. Computes `-self`, returning `None` if `self == i32::MIN`.
///
/// # Example
///
/// ```
/// #![feature(nonzero_negation_ops)]
///
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("let pos_five = ", stringify!($Ty), "::new(5)?;")]
#[doc = concat!("let neg_five = ", stringify!($Ty), "::new(-5)?;")]
#[doc = concat!("let min = ", stringify!($Ty), "::new(",
stringify!($Int), "::MIN)?;")]
///
/// assert_eq!(pos_five.checked_neg(), Some(neg_five));
/// assert_eq!(min.checked_neg(), None);
/// # Some(())
/// # }
/// ```
#[inline]
#[unstable(feature = "nonzero_negation_ops", issue = "102443")]
pub const fn checked_neg(self) -> Option<$Ty> {
if let Some(result) = self.get().checked_neg() {
// SAFETY: negation of nonzero cannot yield zero values.
return Some(unsafe { $Ty::new_unchecked(result) });
}
None
}
/// Negates self, overflowing if this is equal to the minimum value.
///
#[doc = concat!("See [`", stringify!($Int), "::overflowing_neg`]")]
/// for documentation on overflow behaviour.
///
/// # Example
///
/// ```
/// #![feature(nonzero_negation_ops)]
///
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("let pos_five = ", stringify!($Ty), "::new(5)?;")]
#[doc = concat!("let neg_five = ", stringify!($Ty), "::new(-5)?;")]
#[doc = concat!("let min = ", stringify!($Ty), "::new(",
stringify!($Int), "::MIN)?;")]
///
/// assert_eq!(pos_five.overflowing_neg(), (neg_five, false));
/// assert_eq!(min.overflowing_neg(), (min, true));
/// # Some(())
/// # }
/// ```
#[inline]
#[unstable(feature = "nonzero_negation_ops", issue = "102443")]
pub const fn overflowing_neg(self) -> ($Ty, bool) {
let (result, overflow) = self.get().overflowing_neg();
// SAFETY: negation of nonzero cannot yield zero values.
((unsafe { $Ty::new_unchecked(result) }), overflow)
}
/// Saturating negation. Computes `-self`, returning `MAX` if
/// `self == i32::MIN` instead of overflowing.
///
/// # Example
///
/// ```
/// #![feature(nonzero_negation_ops)]
///
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("let pos_five = ", stringify!($Ty), "::new(5)?;")]
#[doc = concat!("let neg_five = ", stringify!($Ty), "::new(-5)?;")]
#[doc = concat!("let min = ", stringify!($Ty), "::new(",
stringify!($Int), "::MIN)?;")]
#[doc = concat!("let min_plus_one = ", stringify!($Ty), "::new(",
stringify!($Int), "::MIN + 1)?;")]
#[doc = concat!("let max = ", stringify!($Ty), "::new(",
stringify!($Int), "::MAX)?;")]
///
/// assert_eq!(pos_five.saturating_neg(), neg_five);
/// assert_eq!(min.saturating_neg(), max);
/// assert_eq!(max.saturating_neg(), min_plus_one);
/// # Some(())
/// # }
/// ```
#[inline]
#[unstable(feature = "nonzero_negation_ops", issue = "102443")]
pub const fn saturating_neg(self) -> $Ty {
if let Some(result) = self.checked_neg() {
return result;
}
$Ty::MAX
}
/// Wrapping (modular) negation. Computes `-self`, wrapping around at the boundary
/// of the type.
///
#[doc = concat!("See [`", stringify!($Int), "::wrapping_neg`]")]
/// for documentation on overflow behaviour.
///
/// # Example
///
/// ```
/// #![feature(nonzero_negation_ops)]
///
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("let pos_five = ", stringify!($Ty), "::new(5)?;")]
#[doc = concat!("let neg_five = ", stringify!($Ty), "::new(-5)?;")]
#[doc = concat!("let min = ", stringify!($Ty), "::new(",
stringify!($Int), "::MIN)?;")]
///
/// assert_eq!(pos_five.wrapping_neg(), neg_five);
/// assert_eq!(min.wrapping_neg(), min);
/// # Some(())
/// # }
/// ```
#[inline]
#[unstable(feature = "nonzero_negation_ops", issue = "102443")]
pub const fn wrapping_neg(self) -> $Ty {
let result = self.get().wrapping_neg();
// SAFETY: negation of nonzero cannot yield zero values.
unsafe { $Ty::new_unchecked(result) }
}
}
)+
}