1 files changed, 142 insertions, 0 deletions
diff --git a/vendor/itertools/src/intersperse.rs b/vendor/itertools/src/intersperse.rs
new file mode 100644
index 00000000..5f4f7938
--- /dev/null
+++ b/vendor/itertools/src/intersperse.rs
@@ -0,0 +1,142 @@
+use super::size_hint;
+use std::iter::{Fuse, FusedIterator};
+
+pub trait IntersperseElement<Item> {
+    fn generate(&mut self) -> Item;
+}
+
+#[derive(Debug, Clone)]
+pub struct IntersperseElementSimple<Item>(Item);
+
+impl<Item: Clone> IntersperseElement<Item> for IntersperseElementSimple<Item> {
+    fn generate(&mut self) -> Item {
+        self.0.clone()
+    }
+}
+
+/// An iterator adaptor to insert a particular value
+/// between each element of the adapted iterator.
+///
+/// Iterator element type is `I::Item`
+///
+/// This iterator is *fused*.
+///
+/// See [`.intersperse()`](crate::Itertools::intersperse) for more information.
+pub type Intersperse<I> = IntersperseWith<I, IntersperseElementSimple<<I as Iterator>::Item>>;
+
+/// Create a new Intersperse iterator
+pub fn intersperse<I>(iter: I, elt: I::Item) -> Intersperse<I>
+where
+    I: Iterator,
+{
+    intersperse_with(iter, IntersperseElementSimple(elt))
+}
+
+impl<Item, F: FnMut() -> Item> IntersperseElement<Item> for F {
+    fn generate(&mut self) -> Item {
+        self()
+    }
+}
+
+/// An iterator adaptor to insert a particular value created by a function
+/// between each element of the adapted iterator.
+///
+/// Iterator element type is `I::Item`
+///
+/// This iterator is *fused*.
+///
+/// See [`.intersperse_with()`](crate::Itertools::intersperse_with) for more information.
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Clone, Debug)]
+pub struct IntersperseWith<I, ElemF>
+where
+    I: Iterator,
+{
+    element: ElemF,
+    iter: Fuse<I>,
+    /// `peek` is None while no item have been taken out of `iter` (at definition).
+    /// Then `peek` will alternatively be `Some(None)` and `Some(Some(item))`,
+    /// where `None` indicates it's time to generate from `element` (unless `iter` is empty).
+    peek: Option<Option<I::Item>>,
+}
+
+/// Create a new `IntersperseWith` iterator
+pub fn intersperse_with<I, ElemF>(iter: I, elt: ElemF) -> IntersperseWith<I, ElemF>
+where
+    I: Iterator,
+{
+    IntersperseWith {
+        peek: None,
+        iter: iter.fuse(),
+        element: elt,
+    }
+}
+
+impl<I, ElemF> Iterator for IntersperseWith<I, ElemF>
+where
+    I: Iterator,
+    ElemF: IntersperseElement<I::Item>,
+{
+    type Item = I::Item;
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        let Self {
+            element,
+            iter,
+            peek,
+        } = self;
+        match peek {
+            Some(item @ Some(_)) => item.take(),
+            Some(None) => match iter.next() {
+                new @ Some(_) => {
+                    *peek = Some(new);
+                    Some(element.generate())
+                }
+                None => None,
+            },
+            None => {
+                *peek = Some(None);
+                iter.next()
+            }
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let mut sh = self.iter.size_hint();
+        sh = size_hint::add(sh, sh);
+        match self.peek {
+            Some(Some(_)) => size_hint::add_scalar(sh, 1),
+            Some(None) => sh,
+            None => size_hint::sub_scalar(sh, 1),
+        }
+    }
+
+    fn fold<B, F>(self, init: B, mut f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        let Self {
+            mut element,
+            mut iter,
+            peek,
+        } = self;
+        let mut accum = init;
+
+        if let Some(x) = peek.unwrap_or_else(|| iter.next()) {
+            accum = f(accum, x);
+        }
+
+        iter.fold(accum, |accum, x| {
+            let accum = f(accum, element.generate());
+            f(accum, x)
+        })
+    }
+}
+
+impl<I, ElemF> FusedIterator for IntersperseWith<I, ElemF>
+where
+    I: Iterator,
+    ElemF: IntersperseElement<I::Item>,
+{
+}