Introduce or_item functions to IteratorExt.

README.md

@@ -42,6 +42,19 @@ let xs = Vec1::from([0i32, 1, 2]);
 let ys: Vec1<_> = xs.into_iter1().map(|x| x + 1).collect();
 ```
 
+Bridging between `Iterator` and `Iterator1`:
+
+```rust
+use mitsein::iter1;
+use mitsein::prelude::*;
+use mitsein::vec1::Vec1;
+
+let xs = iter1::from_head_and_tail(0i32, [1, 2]);
+let xs: Vec1<_> = xs.into_iter().skip(3).or_item(3).collect();
+
+assert_eq!(xs.as_slice(), &[3]);
+```
+
 ## Features and Comparisons
 
 By providing non-empty APIs over both collections **and** views (i.e., slices

src/iter1.rs

@@ -25,6 +25,15 @@ pub trait IteratorExt: Iterator {
     where
         Self: Sized,
         T: IntoIterator1<Item = Self::Item>;
+
+    fn or_item(self, item: Self::Item) -> OrItem<Self>
+    where
+        Self: Sized;
+
+    fn or_else_item<F>(self, f: F) -> OrElseItem<Self, F>
+    where
+        Self: Sized,
+        F: FnInto<Into = Self::Item>;
 }
 
 impl<I> IteratorExt for I
@@ -41,6 +50,23 @@ where
     {
         Iterator1::from_iter_unchecked(self.chain(items.into_iter1()))
     }
+
+    fn or_item(self, item: Self::Item) -> OrItem<Self> {
+        match Iterator1::try_from_iter(self) {
+            Ok(items) => items.chain(None),
+            Err(empty) => Iterator1::from_iter_unchecked(empty.chain(Some(item))),
+        }
+    }
+
+    fn or_else_item<F>(self, f: F) -> OrElseItem<Self, F>
+    where
+        F: FnInto<Into = Self::Item>,
+    {
+        match Iterator1::try_from_iter(self) {
+            Ok(items) => items.chain(AtMostOneWith::none()),
+            Err(empty) => Iterator1::from_iter_unchecked(empty.chain(AtMostOneWith::some(f))),
+        }
+    }
 }
 
 pub trait FromIterator1<T> {