Rollup merge of rust-lang#63442 - lzutao:vec-bin-search-insert, r=Mar…

…k-Simulacrum

Add an example to show how to insert item to a sorted vec

Closes rust-lang#61684
cc rust-lang#61742
r? @Mark-Simulacrum, @jonas-schievink

src/libcore/slice/mod.rs

@@ -1364,6 +1364,17 @@ impl<T> [T] {
     /// let r = s.binary_search(&1);
     /// assert!(match r { Ok(1..=4) => true, _ => false, });
     /// ```
+    ///
+    /// If you want to insert an item to a sorted vector, while maintaining
+    /// sort order:
+    ///
+    /// ```
+    /// let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
+    /// let num = 42;
+    /// let idx = s.binary_search(&num).unwrap_or_else(|x| x);
+    /// s.insert(idx, num);
+    /// assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn binary_search(&self, x: &T) -> Result<usize, usize>
         where T: Ord