From 152f9b5c2bac34bad7b164455953bfc56fa00967 Mon Sep 17 00:00:00 2001
From: Matthias Beyer <mail@beyermatthias.de>
Date: Thu, 1 Feb 2018 16:02:33 +0100
Subject: Add convenience helper for filtering iterators

---
 src/iter.rs | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs  |  1 +
 2 files changed, 65 insertions(+)
 create mode 100644 src/iter.rs

diff --git a/src/iter.rs b/src/iter.rs
new file mode 100644
index 0000000..79675d1
--- /dev/null
+++ b/src/iter.rs
@@ -0,0 +1,64 @@
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+
+use filter::Filter;
+
+pub struct FilteredIterator<T, F, I>(F, I)
+    where F: Filter<T>,
+          I: Iterator<Item = T>;
+
+impl<T, F, I> Iterator for FilteredIterator<T, F, I>
+    where F: Filter<T>,
+          I: Iterator<Item = T>
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        while let Some(next) = self.1.next() {
+            if self.0.filter(&next) {
+                return Some(next);
+            }
+        }
+
+        None
+    }
+}
+
+pub trait FilterWith<T, F: Filter<T>> : Iterator<Item = T> + Sized {
+    fn filter_with(self, f: F) -> FilteredIterator<T, F, Self>;
+}
+
+impl<I, T, F: Filter<T>> FilterWith<T, F> for I
+    where I: Iterator<Item = T>
+{
+    fn filter_with(self, f: F) -> FilteredIterator<T, F, Self> {
+        FilteredIterator(f, self)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_filter_with() {
+        struct Foo;
+        impl Filter<u64> for Foo {
+            fn filter(&self, u: &u64) -> bool {
+                *u > 5
+            }
+        }
+
+        let foo = Foo;
+
+        let v : Vec<u64> = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
+            .into_iter()
+            .filter_with(foo)
+            .collect();
+
+        assert_eq!(v, vec![6, 7, 8, 9]);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 7da2cc5..ff5d7ac 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -78,5 +78,6 @@
 pub mod impl_traits;
 pub mod filter;
 pub mod failable;
+pub mod iter;
 pub mod ops;
 
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