1 files changed, 36 insertions, 0 deletions
diff --git a/library/core/src/num/f64.rs b/library/core/src/num/f64.rs
index 1e7387217cb..3aafc435f1e 100644
--- a/library/core/src/num/f64.rs
+++ b/library/core/src/num/f64.rs
@@ -951,6 +951,42 @@ impl f64 {
         }
     }
 
+    /// Calculates the middle point of `self` and `rhs`.
+    ///
+    /// This returns NaN when *either* argument is NaN or if a combination of
+    /// +inf and -inf is provided as arguments.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(num_midpoint)]
+    /// assert_eq!(1f64.midpoint(4.0), 2.5);
+    /// assert_eq!((-5.5f64).midpoint(8.0), 1.25);
+    /// ```
+    #[unstable(feature = "num_midpoint", issue = "110840")]
+    pub fn midpoint(self, other: f64) -> f64 {
+        const LO: f64 = f64::MIN_POSITIVE * 2.;
+        const HI: f64 = f64::MAX / 2.;
+
+        let (a, b) = (self, other);
+        let abs_a = a.abs_private();
+        let abs_b = b.abs_private();
+
+        if abs_a <= HI && abs_b <= HI {
+            // Overflow is impossible
+            (a + b) / 2.
+        } else if abs_a < LO {
+            // Not safe to halve a
+            a + (b / 2.)
+        } else if abs_b < LO {
+            // Not safe to halve b
+            (a / 2.) + b
+        } else {
+            // Not safe to halve a and b
+            (a / 2.) + (b / 2.)
+        }
+    }
+
     /// Rounds toward zero and converts to any primitive integer type,
     /// assuming that the value is finite and fits in that type.
     ///