.

src/extensions/sequence.rs

@@ -726,7 +726,6 @@ pub trait Sequence<Item> {
     self.into_iter().zip(elements).flat_map(|(item1, item2)| iter::once(item1).chain(iter::once(item2))).collect()
   }
 
-  // FIXME - fix the failing test case
   /// Creates a new sequence which places a copy of `separator` between
   /// elements of the original sequence with the distance between the inserted
   /// values determined by the specified `interval`.
@@ -744,12 +743,12 @@ pub trait Sequence<Item> {
   /// # let a_source = vec![1, 2, 3];
   /// let a = vec![1, 2, 3];
   ///
-  /// // assert_eq!(a.intersperse(1, 0), vec![1, 0, 2, 0, 3]);
+  /// assert_eq!(a.intersperse(1, 0), vec![1, 0, 2, 0, 3]);
   /// # let a = a_source.clone();
-  /// // assert_eq!(a.intersperse(2, 0), vec![1, 2, 0, 3]);
+  /// assert_eq!(a.intersperse(2, 0), vec![1, 2, 0, 3]);
   ///
   /// # let a = a_source.clone();
-  /// // assert_eq!(a.intersperse(3, 0), vec![1, 2, 3]);
+  /// assert_eq!(a.intersperse(3, 0), vec![1, 2, 3]);
   /// ```
   #[inline]
   fn intersperse(self, interval: usize, element: Item) -> Self
@@ -760,7 +759,6 @@ pub trait Sequence<Item> {
     self.intersperse_with(interval, || element.clone())
   }
 
-  // FIXME - fix the failing test case
   /// Creates a new sequence which places a value generated by `to_element`
   /// between elements of the original sequence with the distance between the
   /// inserted values determined by the specified `interval`.
@@ -778,12 +776,12 @@ pub trait Sequence<Item> {
   /// # let a_source = vec![1, 2, 3];
   /// let a = vec![1, 2, 3];
   ///
-  /// // assert_eq!(a.intersperse_with(1, || 0), vec![1, 0, 2, 0, 3]);
+  /// assert_eq!(a.intersperse_with(1, || 0), vec![1, 0, 2, 0, 3]);
   /// # let a = a_source.clone();
-  /// // assert_eq!(a.intersperse_with(2, || 0), vec![1, 2, 0, 3]);
+  /// assert_eq!(a.intersperse_with(2, || 0), vec![1, 2, 0, 3]);
   ///
   /// # let a = a_source.clone();
-  /// // assert_eq!(a.intersperse_with(3, || 0), vec![1, 2, 3]);
+  /// assert_eq!(a.intersperse_with(3, || 0), vec![1, 2, 3]);
   /// ```
   fn intersperse_with(self, interval: usize, mut to_value: impl FnMut() -> Item) -> Self
   where
@@ -792,18 +790,21 @@ pub trait Sequence<Item> {
   {
     assert_ne!(interval, 0, "interval must be non-zero");
     let mut iterator = self.into_iter();
-    let mut value = iter::repeat(to_value());
     let mut index = 0_usize;
-    let mut inserted = false;
+    let mut stored: Option<Item> = None;
     unfold(|| {
-      if !inserted && index % interval == 0 {
-        inserted = true;
-        value.next()
-      } else {
-        inserted = false;
-        index += 1;
-        iterator.next()
-      }
+      stored.take().or_else(|| {
+        iterator.next().map(|item| {
+          let new_item = if index % interval == 0 && index != 0 {
+            stored = Some(item);
+            to_value()
+          } else {
+            item
+          };
+          index += 1;
+          new_item
+        })
+      })
     })
     .collect()
   }

tests/extensions/sequence.rs

@@ -207,23 +207,23 @@ where
   assert_seq_equal(a.interleave_exact(vec![]), vec![]);
   assert_seq_equal(e.interleave_exact(vec![1]), vec![]);
 
-  // intersperse - FIXME - fix the failing test case
-  // let a = a_source.clone();
-  // let e = e_source.clone();
-  // assert_seq_equal(a.intersperse(1, 0), vec![1, 0, 2, 0, 3]);
-  // let a = a_source.clone();
-  // assert_seq_equal(a.intersperse(2, 0), vec![1, 2, 0, 3]);
-  // let a = a_source.clone();
-  // assert_seq_equal(a.intersperse(3, 0), vec![1, 2, 3]);
-  // assert_seq_equal(e.intersperse(1, 0), vec![]);
+  // intersperse
+  let a = a_source.clone();
+  let e = e_source.clone();
+  assert_seq_equal(a.intersperse(1, 0), vec![1, 0, 2, 0, 3]);
+  let a = a_source.clone();
+  assert_seq_equal(a.intersperse(2, 0), vec![1, 2, 0, 3]);
+  let a = a_source.clone();
+  assert_seq_equal(a.intersperse(3, 0), vec![1, 2, 3]);
+  assert_seq_equal(e.intersperse(1, 0), vec![]);
 
-  // intersperse_with - FIXME - fix the failing test case
-  // let a = a_source.clone();
-  // let e = e_source.clone();
-  // assert_seq_equal(a.intersperse_with(2, || 0), vec![1, 2, 0, 3]);
-  // let a = a_source.clone();
-  // assert_seq_equal(a.intersperse_with(3, || 0), vec![1, 2, 3]);
-  // assert_seq_equal(e.intersperse_with(1, || 0), vec![]);
+  // intersperse_with
+  let a = a_source.clone();
+  let e = e_source.clone();
+  assert_seq_equal(a.intersperse_with(2, || 0), vec![1, 2, 0, 3]);
+  let a = a_source.clone();
+  assert_seq_equal(a.intersperse_with(3, || 0), vec![1, 2, 3]);
+  assert_seq_equal(e.intersperse_with(1, || 0), vec![]);
 
   // map_while - FIXME - implement test
   // assert_seq_equal(a.map_while(|&x| if x < 2 { Some(x + 1) } else { None }), vec![2, 3]);