Add filter map functions

2 files changed, 36 insertions, 0 deletions

diff --git a/src/ops/map.rs b/src/ops/map.rs
new file mode 100644
index 0000000..b7a2028
--- /dev/null
+++ b/src/ops/map.rs
@@ -0,0 +1,35 @@
+//
+// 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/.
+//
+
+//! Map implementation.
+//!
+//! Will be automatically included when incluing `filter::Filter`, so importing this module
+//! shouldn't be necessary.
+//!
+use std::marker::PhantomData;
+use std::borrow::Borrow;
+
+use filter::Filter;
+
+#[must_use = "filters are lazy and do nothing unless consumed"]
+#[derive(Clone)]
+pub struct MapInput<F, M, FT, B>(F, M, PhantomData<FT>, PhantomData<B>);
+
+impl<F, M, FT, B> MapInput<F, M, FT, B> {
+    pub fn new(a: F, m: M) -> MapInput<F, M, FT, B> {
+        MapInput(a, m, PhantomData, PhantomData)
+    }
+}
+
+impl<FT, F, T, B, M> Filter<T> for MapInput<F, M, FT, B>
+    where F: Filter<FT>,
+          B: Borrow<FT> + Sized,
+          M: Fn(&T) -> B
+{
+    fn filter(&self, e: &T) -> bool {
+        self.0.filter(self.1(e).borrow())
+    }
+}
diff --git a/src/ops/mod.rs b/src/ops/mod.rs
index d152cce..a5dd6b6 100644
--- a/src/ops/mod.rs
+++ b/src/ops/mod.rs
@@ -9,3 +9,4 @@ pub mod bool;
 pub mod not;
 pub mod or;
 pub mod xor;
+pub mod map;