Improved docstrings for free::chain

- Improved the description of the function and added example.
- Fixed errors in PR
- Implemented suggestions by phimuemue

src/free.rs

@@ -128,17 +128,23 @@ pub fn zip<I, J>(i: I, j: J) -> Zip<I::IntoIter, J::IntoIter>
     i.into_iter().zip(j)
 }
 
-/// Create an iterator that first iterates `i` and then `j`.
+
+/// Takes two iterators and creates a new iterator over both in sequence. 
 ///
 /// [`IntoIterator`] enabled version of [`Iterator::chain`].
 ///
+/// ## Example
 /// ```
 /// use itertools::chain;
+/// 
+/// let mut result:Vec<i32> = Vec::new();
 ///
-/// for elt in chain(&[1, 2, 3], &[4]) {
-///     /* loop body */
+/// for element in chain(&[1, 2, 3] , &[4]) {
+///     result.push(*element);
 /// }
+/// assert_eq!(result, vec![1, 2, 3, 4]);
 /// ```
+#[deprecated(note="Use std::iter::Chain instead", since="1.0.0")]
 pub fn chain<I, J>(i: I, j: J) -> iter::Chain<<I as IntoIterator>::IntoIter, <J as IntoIterator>::IntoIter>
     where I: IntoIterator,
           J: IntoIterator<Item = I::Item>

src/lib.rs

@@ -2271,15 +2271,15 @@ pub trait Itertools : Iterator {
     /// ```
     ///
     /// Which, for non-associative functions, will typically produce a different
-    /// result than the linear call tree used by `fold1`:
+    /// result than the linear call tree used by [`Iterator::reduce`]:
     ///
     /// ```text
     /// 1 2 3 4 5 6 7
     /// │ │ │ │ │ │ │
     /// └─f─f─f─f─f─f
     /// ```
     ///
-    /// If `f` is associative, prefer the normal `fold1` instead.
+    /// If `f` is associative, prefer the normal [`Iterator::reduce`] instead.
     ///
     /// ```
     /// use itertools::Itertools;