From cdc6afed389ecdcea0955eadae59ea6b008a58fe Mon Sep 17 00:00:00 2001
From: Jethro Beekman <jethro@jbeekman.nl>
Date: Tue, 26 Jul 2016 16:31:39 -0700
Subject: [PATCH] Add non-panicking abs() functions to all signed integer
 types.

Currently, calling abs() on one of the signed integer types might panic (in
debug mode at least) because the absolute value of the largest negative value
can not be represented in that signed type. Unlike all other integer
operations, there is currently not a non-panicking version on this function.
This seems to just be an oversight in the design, therefore just adding it now.
---
 src/libcore/num/mod.rs | 84 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 97648cc3469..4636811aa46 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -611,6 +611,31 @@ pub fn checked_shr(self, rhs: u32) -> Option<Self> {
             if b {None} else {Some(a)}
         }
 
+        /// Checked absolute value. Computes `self.abs()`, returning `None` if
+        /// `self == MIN`.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// # #![feature(no_panic_abs)]
+        ///
+        /// use std::i32;
+        ///
+        /// assert_eq!((-5i32).checked_abs(), Some(5));
+        /// assert_eq!(i32::MIN.checked_abs(), None);
+        /// ```
+        #[unstable(feature = "no_panic_abs", issue = "35057")]
+        #[inline]
+        pub fn checked_abs(self) -> Option<Self> {
+            if self.is_negative() {
+                self.checked_neg()
+            } else {
+                Some(self)
+            }
+        }
+
         /// Saturating integer addition. Computes `self + other`, saturating at
         /// the numeric bounds instead of overflowing.
         ///
@@ -863,6 +888,36 @@ pub fn wrapping_shr(self, rhs: u32) -> Self {
             self.overflowing_shr(rhs).0
         }
 
+        /// Wrapping (modular) absolute value. Computes `self.abs()`,
+        /// wrapping around at the boundary of the type.
+        ///
+        /// The only case where such wrapping can occur is when one takes
+        /// the absolute value of the negative minimal value for the type
+        /// this is a positive value that is too large to represent in the
+        /// type. In such a case, this function returns `MIN` itself.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// # #![feature(no_panic_abs)]
+        ///
+        /// assert_eq!(100i8.wrapping_abs(), 100);
+        /// assert_eq!((-100i8).wrapping_abs(), 100);
+        /// assert_eq!((-128i8).wrapping_abs(), -128);
+        /// assert_eq!((-128i8).wrapping_abs() as u8, 128);
+        /// ```
+        #[unstable(feature = "no_panic_abs", issue = "35057")]
+        #[inline(always)]
+        pub fn wrapping_abs(self) -> Self {
+            if self.is_negative() {
+                self.wrapping_neg()
+            } else {
+                self
+            }
+        }
+
         /// Calculates `self` + `rhs`
         ///
         /// Returns a tuple of the addition along with a boolean indicating
@@ -1071,6 +1126,35 @@ pub fn overflowing_shr(self, rhs: u32) -> (Self, bool) {
             (self >> (rhs & ($BITS - 1)), (rhs > ($BITS - 1)))
         }
 
+        /// Computes the absolute value of `self`.
+        ///
+        /// Returns a tuple of the absolute version of self along with a
+        /// boolean indicating whether an overflow happened. If self is the
+        /// minimum value (e.g. i32::MIN for values of type i32), then the
+        /// minimum value will be returned again and true will be returned for
+        /// an overflow happening.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// # #![feature(no_panic_abs)]
+        ///
+        /// assert_eq!(10i8.overflowing_abs(), (10,false));
+        /// assert_eq!((-10i8).overflowing_abs(), (10,false));
+        /// assert_eq!((-128i8).overflowing_abs(), (-128,true));
+        /// ```
+        #[unstable(feature = "no_panic_abs", issue = "35057")]
+        #[inline]
+        pub fn overflowing_abs(self) -> (Self, bool) {
+            if self.is_negative() {
+                self.overflowing_neg()
+            } else {
+                (self, false)
+            }
+        }
+
         /// Raises self to the power of `exp`, using exponentiation by squaring.
         ///
         /// # Examples
-- 
2.44.0