Merge pull request #30 from cuviper/rfold

Implement and use DoubleEndedIterator::rfold
sfackler · Sep 7, 2022 · a0f4ee0 · a0f4ee0
2 parents f93531c + 3bd3360
commit a0f4ee0
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Showing 2 changed files with 56 additions and 7 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -884,6 +884,15 @@ where
     fn next_back(&mut self) -> Option<I::Item> {
         self.0.next_back().map(Clone::clone)
     }
+
+    #[inline]
+    fn rfold<Acc, Fold>(self, init: Acc, mut f: Fold) -> Acc
+    where
+        Self: Sized,
+        Fold: FnMut(Acc, Self::Item) -> Acc,
+    {
+        self.0.rfold(init, move |acc, item| f(acc, item.clone()))
+    }
 }
 
 /// A streaming iterator which filters the elements of a streaming iterator with a predicate.
@@ -1313,6 +1322,19 @@ where
 
         None
     }
+
+    #[inline]
+    fn rfold<Acc, Fold>(self, init: Acc, mut f: Fold) -> Acc
+    where
+        Self: Sized,
+        Fold: FnMut(Acc, Self::Item) -> Acc,
+    {
+        let mut map = self.f;
+        self.it.rfold(init, move |acc, item| match map(item) {
+            Some(mapped) => f(acc, mapped),
+            None => acc,
+        })
+    }
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -1705,6 +1727,16 @@ where
     fn next_back(&mut self) -> Option<Self::Item> {
         self.it.next_back().map(&mut self.f)
     }
+
+    #[inline]
+    fn rfold<Acc, Fold>(self, init: Acc, mut f: Fold) -> Acc
+    where
+        Self: Sized,
+        Fold: FnMut(Acc, Self::Item) -> Acc,
+    {
+        let mut map = self.f;
+        self.it.rfold(init, move |acc, item| f(acc, map(item)))
+    }
 }
 
 /// A regular, non-streaming iterator which transforms the elements of a mutable streaming iterator.
@@ -1751,6 +1783,16 @@ where
     fn next_back(&mut self) -> Option<Self::Item> {
         self.it.next_back_mut().map(&mut self.f)
     }
+
+    #[inline]
+    fn rfold<Acc, Fold>(self, init: Acc, mut f: Fold) -> Acc
+    where
+        Self: Sized,
+        Fold: FnMut(Acc, Self::Item) -> Acc,
+    {
+        let mut map = self.f;
+        self.it.rfold_mut(init, move |acc, item| f(acc, map(item)))
+    }
 }
 
 /// A streaming iterator which transforms the elements of a streaming iterator.
@@ -1849,6 +1891,15 @@ where
     fn next_back(&mut self) -> Option<<I::Item as ToOwned>::Owned> {
         self.0.next_back().map(ToOwned::to_owned)
     }
+
+    #[inline]
+    fn rfold<Acc, Fold>(self, init: Acc, mut f: Fold) -> Acc
+    where
+        Self: Sized,
+        Fold: FnMut(Acc, Self::Item) -> Acc,
+    {
+        self.0.rfold(init, move |acc, item| f(acc, item.to_owned()))
+    }
 }
 
 /// A streaming iterator which skips a number of elements in a streaming iterator.

diff --git a/src/sources.rs b/src/sources.rs
@@ -260,7 +260,7 @@ where
         Self: Sized,
         Fold: FnMut(Acc, &Self::Item) -> Acc,
     {
-        self.it.rev().fold(init, move |acc, item| f(acc, &item))
+        self.it.rfold(init, move |acc, item| f(acc, &item))
     }
 }
 
@@ -293,9 +293,7 @@ where
         Self: Sized,
         F: FnMut(B, &mut Self::Item) -> B,
     {
-        self.it
-            .rev()
-            .fold(init, move |acc, mut item| f(acc, &mut item))
+        self.it.rfold(init, move |acc, mut item| f(acc, &mut item))
     }
 }
 
@@ -360,7 +358,7 @@ where
         Self: Sized,
         Fold: FnMut(Acc, &Self::Item) -> Acc,
     {
-        self.it.rev().fold(init, f)
+        self.it.rfold(init, f)
     }
 }
 
@@ -428,7 +426,7 @@ where
         Self: Sized,
         Fold: FnMut(Acc, &Self::Item) -> Acc,
     {
-        self.it.rev().fold(init, move |acc, item| f(acc, item))
+        self.it.rfold(init, move |acc, item| f(acc, item))
     }
 }
 
@@ -464,7 +462,7 @@ where
         Self: Sized,
         F: FnMut(B, &mut Self::Item) -> B,
     {
-        self.it.rev().fold(init, f)
+        self.it.rfold(init, f)
     }
 }