doc: TreeSet methods and main example.

Author: treeman

src/libcollections/treemap.rs

@@ -138,7 +138,7 @@ impl<K: Ord, V> Default for TreeMap<K,V> {
 }
 
 impl<K: Ord, V> TreeMap<K, V> {
-    /// Create an empty TreeMap
+    /// Create an empty `TreeMap`.
     pub fn new() -> TreeMap<K, V> { TreeMap{root: None, length: 0} }
 
     /// Get a lazy iterator over the keys in the map.
@@ -232,6 +232,7 @@ impl<K, V> TreeMap<K, V> {
     /// Return the value for which `f(key)` returns `Equal`. `f` is invoked
     /// with current key and guides tree navigation. That means `f` should
     /// be aware of natural ordering of the tree.
+    ///
     /// # Example
     ///
     /// ```
@@ -633,15 +634,68 @@ impl<'a, T> Iterator<&'a T> for RevSetItems<'a, T> {
 /// ```{rust}
 /// use std::collections::TreeSet;
 ///
-/// let mut tree_set = TreeSet::new();
+/// let mut set = TreeSet::new();
 ///
-/// tree_set.insert(2i);
-/// tree_set.insert(1i);
-/// tree_set.insert(3i);
+/// set.insert(2i);
+/// set.insert(1i);
+/// set.insert(3i);
 ///
-/// for i in tree_set.iter() {
+/// for i in set.iter() {
 ///    println!("{}", i) // prints 1, then 2, then 3
 /// }
+///
+/// set.remove(&3);
+///
+/// if !set.contains(&3) {
+///     println!("set does not contain a 3 anymore");
+/// }
+/// ```
+///
+/// The easiest way to use `TreeSet` with a custom type is to implement `Ord`.
+/// We must also implement `PartialEq`, `Eq` and `PartialOrd`.
+///
+/// ```
+/// use std::collections::TreeSet;
+///
+/// // We need `Eq` and `PartialEq`, these can be derived.
+/// #[deriving(Eq, PartialEq)]
+/// struct Troll<'a> {
+///     name: &'a str,
+///     level: uint,
+/// }
+///
+/// // Implement `Ord` and sort trolls by level.
+/// impl<'a> Ord for Troll<'a> {
+///     fn cmp(&self, other: &Troll) -> Ordering {
+///         // If we swap `self` and `other`, we get descended ordering.
+///         self.level.cmp(&other.level)
+///     }
+/// }
+///
+/// // `PartialOrd` needs to be implemented as well.
+/// impl<'a> PartialOrd for Troll<'a> {
+///     fn partial_cmp(&self, other: &Troll) -> Option<Ordering> {
+///         Some(self.cmp(other))
+///     }
+/// }
+///
+/// let mut trolls = TreeSet::new();
+///
+/// trolls.insert(Troll { name: "Orgarr", level: 2 });
+/// trolls.insert(Troll { name: "Blargarr", level: 3 });
+/// trolls.insert(Troll { name: "Kron the Smelly One", level: 4 });
+/// trolls.insert(Troll { name: "Wartilda", level: 1 });
+///
+/// println!("You are facing {} trolls!", trolls.len());
+///
+/// // Print the trolls, ordered by level with smallest level first
+/// for x in trolls.iter() {
+///     println!("level {}: {}!", x.level, x.name);
+/// }
+///
+/// // Kill all trolls
+/// trolls.clear();
+/// assert_eq!(trolls.len(), 0);
 /// ```
 #[deriving(Clone)]
 pub struct TreeSet<T> {
@@ -732,25 +786,66 @@ impl<T: Ord> Default for TreeSet<T> {
 }
 
 impl<T: Ord> TreeSet<T> {
-    /// Create an empty TreeSet
+    /// Create an empty `TreeSet`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let mut set: TreeSet<int> = TreeSet::new();
+    /// ```
     #[inline]
     pub fn new() -> TreeSet<T> { TreeSet{map: TreeMap::new()} }
 
-    /// Get a lazy iterator over the values in the set.
-    /// Requires that it be frozen (immutable).
+    /// Get a lazy iterator over the values in the set, in ascending order.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let set: TreeSet<int> = [1i, 4, 3, 5, 2].iter().map(|&x| x).collect();
+    ///
+    /// // Will print in ascending order.
+    /// for x in set.iter() {
+    ///     println!("{}", x);
+    /// }
+    /// ```
     #[inline]
     pub fn iter<'a>(&'a self) -> SetItems<'a, T> {
         SetItems{iter: self.map.iter()}
     }
 
-    /// Get a lazy iterator over the values in the set.
-    /// Requires that it be frozen (immutable).
+    /// Get a lazy iterator over the values in the set, in descending order.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let set: TreeSet<int> = [1i, 4, 3, 5, 2].iter().map(|&x| x).collect();
+    ///
+    /// // Will print in descending order.
+    /// for x in set.rev_iter() {
+    ///     println!("{}", x);
+    /// }
+    /// ```
     #[inline]
     pub fn rev_iter<'a>(&'a self) -> RevSetItems<'a, T> {
         RevSetItems{iter: self.map.rev_iter()}
     }
 
-    /// Get a lazy iterator that consumes the set.
+    /// Creates a consuming iterator, that is, one that moves each value out of the
+    /// set in ascending order. The set cannot be used after calling this.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let set: TreeSet<int> = [1i, 4, 3, 5, 2].iter().map(|&x| x).collect();
+    ///
+    /// // Not possible with a regular `.iter()`
+    /// let v: Vec<int> = set.move_iter().collect();
+    /// assert_eq!(v, vec![1, 2, 3, 4, 5]);
+    /// ```
     #[inline]
     pub fn move_iter(self) -> MoveSetItems<T> {
         self.map.move_iter().map(|(value, _)| value)
@@ -770,24 +865,96 @@ impl<T: Ord> TreeSet<T> {
         SetItems{iter: self.map.upper_bound(v)}
     }
 
-    /// Visit the values (in-order) representing the difference
+    /// Visit the values representing the difference, in ascending order.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let a: TreeSet<int> = [1, 2, 3].iter().map(|&x| x).collect();
+    /// let b: TreeSet<int> = [3, 4, 5].iter().map(|&x| x).collect();
+    ///
+    /// // Can be seen as `a - b`.
+    /// for x in a.difference(&b) {
+    ///     println!("{}", x); // Print 1 then 2
+    /// }
+    ///
+    /// let diff: TreeSet<int> = a.difference(&b).map(|&x| x).collect();
+    /// assert_eq!(diff, [1, 2].iter().map(|&x| x).collect());
+    ///
+    /// // Note that difference is not symmetric,
+    /// // and `b - a` means something else:
+    /// let diff: TreeSet<int> = b.difference(&a).map(|&x| x).collect();
+    /// assert_eq!(diff, [4, 5].iter().map(|&x| x).collect());
+    /// ```
     pub fn difference<'a>(&'a self, other: &'a TreeSet<T>) -> DifferenceItems<'a, T> {
         DifferenceItems{a: self.iter().peekable(), b: other.iter().peekable()}
     }
 
-    /// Visit the values (in-order) representing the symmetric difference
+    /// Visit the values representing the symmetric difference, in ascending order.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let a: TreeSet<int> = [1, 2, 3].iter().map(|&x| x).collect();
+    /// let b: TreeSet<int> = [3, 4, 5].iter().map(|&x| x).collect();
+    ///
+    /// // Print 1, 2, 4, 5 in ascending order.
+    /// for x in a.symmetric_difference(&b) {
+    ///     println!("{}", x);
+    /// }
+    ///
+    /// let diff1: TreeSet<int> = a.symmetric_difference(&b).map(|&x| x).collect();
+    /// let diff2: TreeSet<int> = b.symmetric_difference(&a).map(|&x| x).collect();
+    ///
+    /// assert_eq!(diff1, diff2);
+    /// assert_eq!(diff1, [1, 2, 4, 5].iter().map(|&x| x).collect());
+    /// ```
     pub fn symmetric_difference<'a>(&'a self, other: &'a TreeSet<T>)
         -> SymDifferenceItems<'a, T> {
         SymDifferenceItems{a: self.iter().peekable(), b: other.iter().peekable()}
     }
 
-    /// Visit the values (in-order) representing the intersection
+    /// Visit the values representing the intersection, in ascending order.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::TreeSet;
+    /// let a: TreeSet<int> = [1, 2, 3].iter().map(|&x| x).collect();
+    /// let b: TreeSet<int> = [2, 3, 4].iter().map(|&x| x).collect();
+    ///
+    /// // Print 2, 3 in ascending order.
+    /// for x in a.intersection(&b) {
+    ///     println!("{}", x);
+    /// }
+    ///
+    /// let diff: TreeSet<int> = a.intersection(&b).map(|&x| x).collect();
+    /// assert_eq!(diff, [2, 3].iter().map(|&x| x).collect());
+    /// ```
     pub fn intersection<'a>(&'a self, other: &'a TreeSet<T>)
         -> IntersectionItems<'a, T> {
         IntersectionItems{a: self.iter().peekable(), b: other.iter().peekable()}
     }
 
-    /// Visit the values (in-order) representing the union
+    /// Visit the values representing the union, in ascending order.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::HashSet;
+    /// let a: HashSet<int> = [1, 2, 3].iter().map(|&x| x).collect();
+    /// let b: HashSet<int> = [3, 4, 5].iter().map(|&x| x).collect();
+    ///
+    /// // Print 1, 2, 3, 4, 5 in ascending order.
+    /// for x in a.union(&b) {
+    ///     println!("{}", x);
+    /// }
+    ///
+    /// let diff: HashSet<int> = a.union(&b).map(|&x| x).collect();
+    /// assert_eq!(diff, [1, 2, 3, 4, 5].iter().map(|&x| x).collect());
+    /// ```
     pub fn union<'a>(&'a self, other: &'a TreeSet<T>) -> UnionItems<'a, T> {
         UnionItems{a: self.iter().peekable(), b: other.iter().peekable()}
     }