Import 'num-integer' crate version 0.2.11
Change-Id: I43f7b6de8a4ffae1f721423fce67e56c2137701e
diff --git a/src/average.rs b/src/average.rs
new file mode 100644
index 0000000..29cd11e
--- /dev/null
+++ b/src/average.rs
@@ -0,0 +1,78 @@
+use core::ops::{BitAnd, BitOr, BitXor, Shr};
+use Integer;
+
+/// Provides methods to compute the average of two integers, without overflows.
+pub trait Average: Integer {
+ /// Returns the ceiling value of the average of `self` and `other`.
+ /// -- `⌈(self + other)/2⌉`
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use num_integer::Average;
+ ///
+ /// assert_eq!(( 3).average_ceil(&10), 7);
+ /// assert_eq!((-2).average_ceil(&-5), -3);
+ /// assert_eq!(( 4).average_ceil(& 4), 4);
+ ///
+ /// assert_eq!(u8::max_value().average_ceil(&2), 129);
+ /// assert_eq!(i8::min_value().average_ceil(&-1), -64);
+ /// assert_eq!(i8::min_value().average_ceil(&i8::max_value()), 0);
+ /// ```
+ ///
+ fn average_ceil(&self, other: &Self) -> Self;
+
+ /// Returns the floor value of the average of `self` and `other`.
+ /// -- `⌊(self + other)/2⌋`
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use num_integer::Average;
+ ///
+ /// assert_eq!(( 3).average_floor(&10), 6);
+ /// assert_eq!((-2).average_floor(&-5), -4);
+ /// assert_eq!(( 4).average_floor(& 4), 4);
+ ///
+ /// assert_eq!(u8::max_value().average_floor(&2), 128);
+ /// assert_eq!(i8::min_value().average_floor(&-1), -65);
+ /// assert_eq!(i8::min_value().average_floor(&i8::max_value()), -1);
+ /// ```
+ ///
+ fn average_floor(&self, other: &Self) -> Self;
+}
+
+impl<I> Average for I
+where
+ I: Integer + Shr<usize, Output = I>,
+ for<'a, 'b> &'a I:
+ BitAnd<&'b I, Output = I> + BitOr<&'b I, Output = I> + BitXor<&'b I, Output = I>,
+{
+ // The Henry Gordon Dietz implementation as shown in the Hacker's Delight,
+ // see http://aggregate.org/MAGIC/#Average%20of%20Integers
+
+ /// Returns the floor value of the average of `self` and `other`.
+ #[inline]
+ fn average_floor(&self, other: &I) -> I {
+ (self & other) + ((self ^ other) >> 1)
+ }
+
+ /// Returns the ceil value of the average of `self` and `other`.
+ #[inline]
+ fn average_ceil(&self, other: &I) -> I {
+ (self | other) - ((self ^ other) >> 1)
+ }
+}
+
+/// Returns the floor value of the average of `x` and `y` --
+/// see [Average::average_floor](trait.Average.html#tymethod.average_floor).
+#[inline]
+pub fn average_floor<T: Average>(x: T, y: T) -> T {
+ x.average_floor(&y)
+}
+/// Returns the ceiling value of the average of `x` and `y` --
+/// see [Average::average_ceil](trait.Average.html#tymethod.average_ceil).
+#[inline]
+pub fn average_ceil<T: Average>(x: T, y: T) -> T {
+ x.average_ceil(&y)
+}