add is_disjoint to the Set trait

src/libcore/container.rs

@@ -66,6 +66,10 @@ pub trait Set<T>: Mutable {
     /// present in the set.
     fn remove(&mut self, value: &T) -> bool;
 
+    /// Return true if the set has no elements in common with `other`.
+    /// This is equivalent to checking for an empty intersection.
+    pure fn is_disjoint(&self, other: &self) -> bool;
+
     /// Return true if the set is a subset of another
     pure fn is_subset(&self, other: &self) -> bool;
 

src/libcore/hashmap.rs

@@ -14,16 +14,15 @@
 #[forbid(deprecated_mode)];
 #[forbid(deprecated_pattern)];
 
+use container::{Container, Mutable, Map, Set};
 use cmp::Eq;
 use hash::Hash;
 use to_bytes::IterBytes;
 
 /// Open addressing with linear probing.
 pub mod linear {
+    use super::*;
     use iter::BaseIter;
-    use container::{Container, Mutable, Map, Set};
-    use cmp::Eq;
-    use cmp;
     use hash::Hash;
     use iter;
     use kinds::Copy;
@@ -455,6 +454,12 @@ pub mod linear {
         /// present in the set.
         fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
 
+        /// Return true if the set has no elements in common with `other`.
+        /// This is equivalent to checking for an empty intersection.
+        pure fn is_disjoint(&self, other: &LinearSet<T>) -> bool {
+            iter::all(self, |v| !other.contains(v))
+        }
+
         /// Return true if the set is a subset of another
         pure fn is_subset(&self, other: &LinearSet<T>) -> bool {
             iter::all(self, |v| other.contains(v))
@@ -626,6 +631,28 @@ mod test_map {
 mod test_set {
     use super::*;
 
+    #[test]
+    fn test_disjoint() {
+        let mut xs = linear::LinearSet::new();
+        let mut ys = linear::LinearSet::new();
+        assert xs.is_disjoint(&ys);
+        assert ys.is_disjoint(&xs);
+        assert xs.insert(5);
+        assert ys.insert(11);
+        assert xs.is_disjoint(&ys);
+        assert ys.is_disjoint(&xs);
+        assert xs.insert(7);
+        assert xs.insert(19);
+        assert xs.insert(4);
+        assert ys.insert(2);
+        assert ys.insert(-11);
+        assert xs.is_disjoint(&ys);
+        assert ys.is_disjoint(&xs);
+        assert ys.insert(7);
+        assert !xs.is_disjoint(&ys);
+        assert !ys.is_disjoint(&xs);
+    }
+
     #[test]
     fn test_subset_and_superset() {
         let mut a = linear::LinearSet::new();

src/libstd/treemap.rs

@@ -292,6 +292,33 @@ impl <T: Ord> TreeSet<T>: Set<T> {
     /// present in the set.
     fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
 
+    /// Return true if the set has no elements in common with `other`.
+    /// This is equivalent to checking for an empty intersection.
+    pure fn is_disjoint(&self, other: &TreeSet<T>) -> bool {
+        let mut x = self.iter();
+        let mut y = other.iter();
+        unsafe { // purity workaround
+            x = x.next();
+            y = y.next();
+            let mut a = x.get();
+            let mut b = y.get();
+            while a.is_some() && b.is_some() {
+                let a1 = a.unwrap();
+                let b1 = b.unwrap();
+                if a1 < b1 {
+                    x = x.next();
+                    a = x.get();
+                } else if b1 < a1 {
+                    y = y.next();
+                    b = y.get();
+                } else {
+                    return false;
+                }
+            }
+        }
+        true
+    }
+
     /// Return true if the set is a subset of another
     pure fn is_subset(&self, other: &TreeSet<T>) -> bool {
         other.is_superset(self)
@@ -345,33 +372,6 @@ impl <T: Ord> TreeSet<T> {
         TreeSetIterator{iter: self.map.iter()}
     }
 
-    /// Return true if the set has no elements in common with `other`.
-    /// This is equivalent to checking for an empty intersection.
-    pure fn is_disjoint(&self, other: &TreeSet<T>) -> bool {
-        let mut x = self.iter();
-        let mut y = other.iter();
-        unsafe { // purity workaround
-            x = x.next();
-            y = y.next();
-            let mut a = x.get();
-            let mut b = y.get();
-            while a.is_some() && b.is_some() {
-                let a1 = a.unwrap();
-                let b1 = b.unwrap();
-                if a1 < b1 {
-                    x = x.next();
-                    a = x.get();
-                } else if b1 < a1 {
-                    y = y.next();
-                    b = y.get();
-                } else {
-                    return false;
-                }
-            }
-        }
-        true
-    }
-
     /// Visit the values (in-order) representing the difference
     pure fn difference(&self, other: &TreeSet<T>, f: fn(&T) -> bool) {
         let mut x = self.iter();