Add bool helper for filter construction

3 files changed, 55 insertions, 0 deletions

diff --git a/src/filter.rs b/src/filter.rs
index c2b887e..388c975 100644
--- a/src/filter.rs
+++ b/src/filter.rs
@@ -2,6 +2,7 @@
 //!
 
 pub use ops::and::And;
+pub use ops::bool::Bool;
 pub use ops::not::Not;
 pub use ops::xor::XOr;
 pub use ops::or::Or;
@@ -189,6 +190,7 @@ pub trait Filter<N> {
 mod test {
     use filter::Filter;
     use ops::and::And;
+    use ops::bool::Bool;
 
     #[test]
     fn closures() {
@@ -252,6 +254,21 @@ mod test {
         assert_eq!(a.filter(&3), false);
     }
 
+    #[test]
+    fn filter_with_bool() {
+        let eq = |&a: &usize| { a == 1 };
+        assert_eq!(eq.and(Bool::new(true)).filter(&0), false);
+
+        let eq = |&a: &usize| { a == 1 };
+        assert_eq!(eq.and(Bool::new(true)).filter(&1), true);
+
+        let eq = |&a: &usize| { a == 1 };
+        assert_eq!(eq.or(Bool::new(true)).filter(&17), true);
+
+        let eq = |&a: &usize| { a == 1 };
+        assert_eq!(eq.or(Bool::new(true)).filter(&42), true);
+    }
+
     struct EqTo {
         pub i: usize,
     }
diff --git a/src/ops/bool.rs b/src/ops/bool.rs
new file mode 100644
index 0000000..fa33da2
--- /dev/null
+++ b/src/ops/bool.rs
@@ -0,0 +1,37 @@
+//! Bool Filter implementation, so we can insert this in filter construction
+//!
+//! Will be automatically included when incluing `filter::Filter`, so importing this module
+//! shouldn't be necessary.
+//!
+use filter::Filter;
+
+#[must_use = "filters are lazy and do nothing unless consumed"]
+#[derive(Clone)]
+pub struct Bool {
+    b: bool
+}
+
+impl Bool {
+
+    pub fn new(b: bool) -> Bool {
+        Bool { b: b }
+    }
+
+}
+
+impl<I> Filter<I> for Bool {
+
+    fn filter(&self, _: &I) -> bool {
+        self.b
+    }
+
+}
+
+impl From<bool> for Bool {
+
+    fn from(b: bool) -> Bool {
+        Bool::new(b)
+    }
+
+}
+
diff --git a/src/ops/mod.rs b/src/ops/mod.rs
index e5881af..4349b89 100644
--- a/src/ops/mod.rs
+++ b/src/ops/mod.rs
@@ -1,4 +1,5 @@
 pub mod and;
+pub mod bool;
 pub mod not;
 pub mod or;
 pub mod xor;