Adds basic filter on Domain

planner/src/solver.rs

@@ -17,13 +17,32 @@ enum Assignment<'a, V> {
 /// The domain of values that can be assigned to variables
 #[derive(Clone)]
 pub struct Domain<V> {
-    values: Vec<V>
+    pub values: Vec<V>
 }
 
 impl<V> Domain<V> {
     pub fn new(values: Vec<V>) -> Domain<V> {
         Domain { values }
     }
+
+    /// Returns a new domain with the given filter applied to inner values
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # extern crate planner;
+    /// # use planner::solver::Domain;
+    /// let domain = Domain::new(vec![1,2,3]);
+    /// fn even(i: &i32) -> bool { i % 2 == 0 };
+    /// assert_eq!(&domain.filter(even).values, &vec![2]);
+    /// ```
+    pub fn filter(&self, f: fn(&V) -> bool) -> Domain<V>
+        where V: std::clone::Clone
+    {
+        Domain {
+            values: self.values.iter().cloned().filter(f).collect(),
+        }
+    }
 }
 
 impl<V: fmt::Debug> fmt::Debug for Domain<V> {
@@ -32,7 +51,7 @@ impl<V: fmt::Debug> fmt::Debug for Domain<V> {
     }
 }
 
-type Constraint<'a,V> = fn(&Variables<'a,V>) -> bool;
+pub type Constraint<'a,V> = fn(&Variables<'a,V>) -> bool;
 
 pub struct Problem<'a, V> {
     /// The initial assignements map