From: Alissa Rao <lymia@lymiahugs.com>
Date: Mon, 4 Apr 2022 08:00:13 +0000 (-0700)
Subject: Implement DoubleEndedIterator for EnumSet.
X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;h=a288b5a09b49e49b332d0bf9962ac668e2a4b61d;p=enumset.git

Implement DoubleEndedIterator for EnumSet.
---

diff --git a/enumset/src/lib.rs b/enumset/src/lib.rs
index 0ff95fb..5a137c3 100644
--- a/enumset/src/lib.rs
+++ b/enumset/src/lib.rs
@@ -693,6 +693,7 @@ impl <T: EnumSetType> EnumSetIter<T> {
         EnumSetIter { set }
     }
 }
+
 impl <T: EnumSetType> Iterator for EnumSetIter<T> {
     type Item = T;
 
@@ -711,6 +712,18 @@ impl <T: EnumSetType> Iterator for EnumSetIter<T> {
     }
 }
 
+impl <T: EnumSetType> DoubleEndedIterator for EnumSetIter<T> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        if self.set.is_empty() {
+            None
+        } else {
+            let bit = T::Repr::WIDTH - 1 - self.set.__priv_repr.leading_zeros();
+            self.set.__priv_repr.remove_bit(bit);
+            unsafe { Some(T::enum_from_u32(bit)) }
+        }
+    }
+}
+
 impl<T: EnumSetType> ExactSizeIterator for EnumSetIter<T> {}
 
 impl<T: EnumSetType> Extend<T> for EnumSet<T> {
diff --git a/enumset/tests/ops.rs b/enumset/tests/ops.rs
index 2dbf6e8..0e71378 100644
--- a/enumset/tests/ops.rs
+++ b/enumset/tests/ops.rs
@@ -206,10 +206,14 @@ macro_rules! test_enum {
             let set_a = $e::A | $e::B | $e::E;
             let vec_a: Vec<_> = set_a.iter().collect();
             assert_eq!(vec_a, &[$e::A, $e::B, $e::E]);
-
-            let set_a = $e::B | $e::D | $e::G;
-            let vec_a: Vec<_> = set_a.iter().collect();
-            assert_eq!(vec_a, &[$e::B, $e::D, $e::G]);
+            let vec_a_rev: Vec<_> = set_a.iter().rev().collect();
+            assert_eq!(vec_a_rev, &[$e::E, $e::B, $e::A]);
+
+            let set_b = $e::B | $e::C | $e::D | $e::G;
+            let vec_b: Vec<_> = set_b.iter().collect();
+            assert_eq!(vec_b, &[$e::B, $e::C, $e::D, $e::G]);
+            let vec_b_rev: Vec<_> = set_b.iter().rev().collect();
+            assert_eq!(vec_b_rev, &[$e::G, $e::D, $e::C, $e::B]);
         }
 
         fn check_iter_size_hint(set: EnumSet<$e>) {