implement FromIterator also for &Tuple

I'm sick of writing `cloned` =)

Author: nikomatsakis

src/lib.rs

@@ -148,6 +148,15 @@ impl<Tuple: Ord> FromIterator<Tuple> for Relation<Tuple> {
     }
 }
 
+impl<'tuple, Tuple: 'tuple + Copy + Ord> FromIterator<&'tuple Tuple> for Relation<Tuple> {
+    fn from_iter<I>(iterator: I) -> Self
+    where
+        I: IntoIterator<Item = &'tuple Tuple>
+    {
+        Relation::from_vec(iterator.into_iter().cloned().collect())
+    }
+}
+
 impl<Tuple: Ord> std::ops::Deref for Relation<Tuple> {
     type Target = [Tuple];
     fn deref(&self) -> &Self::Target {

src/test.rs

@@ -31,7 +31,7 @@ fn reachable_with_var_join(edges: &[(u32, u32)]) -> Relation<(u32, u32)> {
 
 /// Like `reachable`, but using a relation as an input to `from_join`
 fn reachable_with_relation_join(edges: &[(u32, u32)]) -> Relation<(u32, u32)> {
-    let edges: Relation<_> = edges.iter().cloned().collect();
+    let edges: Relation<_> = edges.iter().collect();
     let mut iteration = Iteration::new();
 
     // NB. Changed from `reachable_with_var_join`: