Add [f32]::sort_floats and [f64]::sort_floats

It's inconvenient to sort a slice or Vec of floats, compared to sorting
integers. To simplify numeric code, add a convenience method to `[f32]`
and `[f64]` to sort them using `sort_unstable_by` with `total_cmp`.

Author: joshtriplett

library/core/src/slice/mod.rs

@@ -4100,6 +4100,66 @@ impl<T, const N: usize> [[T; N]] {
     }
 }
 
+#[cfg(not(bootstrap))]
+#[cfg(not(test))]
+impl [f32] {
+    /// Sorts the slice of floats.
+    ///
+    /// This sort is in-place (i.e. does not allocate), *O*(*n* \* log(*n*)) worst-case, and uses
+    /// the ordering defined by [`f32::total_cmp`].
+    ///
+    /// # Current implementation
+    ///
+    /// This uses the same sorting algorithm as [`sort_unstable_by`](slice::sort_unstable_by).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(sort_floats)]
+    /// let mut v = [2.6, -5e-8, f32::NAN, 8.29, f32::INFINITY, -1.0, 0.0, -f32::INFINITY, -0.0];
+    ///
+    /// v.sort_floats();
+    /// let sorted = [-f32::INFINITY, -1.0, -5e-8, -0.0, 0.0, 2.6, 8.29, f32::INFINITY, f32::NAN];
+    /// assert_eq!(&v[..8], &sorted[..8]);
+    /// assert!(v[8].is_nan());
+    /// ```
+    #[unstable(feature = "sort_floats", issue = "93396")]
+    #[inline]
+    pub fn sort_floats(&mut self) {
+        self.sort_unstable_by(f32::total_cmp);
+    }
+}
+
+#[cfg(not(bootstrap))]
+#[cfg(not(test))]
+impl [f64] {
+    /// Sorts the slice of floats.
+    ///
+    /// This sort is in-place (i.e. does not allocate), *O*(*n* \* log(*n*)) worst-case, and uses
+    /// the ordering defined by [`f64::total_cmp`].
+    ///
+    /// # Current implementation
+    ///
+    /// This uses the same sorting algorithm as [`sort_unstable_by`](slice::sort_unstable_by).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(sort_floats)]
+    /// let mut v = [2.6, -5e-8, f64::NAN, 8.29, f64::INFINITY, -1.0, 0.0, -f64::INFINITY, -0.0];
+    ///
+    /// v.sort_floats();
+    /// let sorted = [-f64::INFINITY, -1.0, -5e-8, -0.0, 0.0, 2.6, 8.29, f64::INFINITY, f64::NAN];
+    /// assert_eq!(&v[..8], &sorted[..8]);
+    /// assert!(v[8].is_nan());
+    /// ```
+    #[unstable(feature = "sort_floats", issue = "93396")]
+    #[inline]
+    pub fn sort_floats(&mut self) {
+        self.sort_unstable_by(f64::total_cmp);
+    }
+}
+
 trait CloneFromSpec<T> {
     fn spec_clone_from(&mut self, src: &[T]);
 }