// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use core::prelude::*;

use core::default::Default;
use core::fmt;
use core::fmt::Show;
use core::iter::Peekable;
use core::iter;
use std::hash::{Writer, Hash};

use tree_map::{TreeMap, Entries, RevEntries, MoveEntries};

// FIXME(conventions): implement bounded iterators
// FIXME(conventions): implement BitOr, BitAnd, BitXor, and Sub
// FIXME(conventions): replace rev_iter(_mut) by making iter(_mut) DoubleEnded

/// An implementation of the `Set` trait on top of the `TreeMap` container. The
/// only requirement is that the type of the elements contained ascribes to the
/// `Ord` trait.
///
/// ## Example
///
/// ```{rust}
/// use std::collections::TreeSet;
///
/// let mut set = TreeSet::new();
///
/// set.insert(2i);
/// set.insert(1i);
/// set.insert(3i);
///
/// 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 descending 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> {
    map: TreeMap<T, ()>
}

impl<T: PartialEq + Ord> PartialEq for TreeSet<T> {
    #[inline]
    fn eq(&self, other: &TreeSet<T>) -> bool { self.map == other.map }
}

impl<T: Eq + Ord> Eq for TreeSet<T> {}

impl<T: Ord> PartialOrd for TreeSet<T> {
    #[inline]
    fn partial_cmp(&self, other: &TreeSet<T>) -> Option<Ordering> {
        self.map.partial_cmp(&other.map)
    }
}

impl<T: Ord> Ord for TreeSet<T> {
    #[inline]
    fn cmp(&self, other: &TreeSet<T>) -> Ordering {
        iter::order::cmp(self.iter(), other.iter())
    }
}

impl<T: Ord + Show> Show for TreeSet<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        try!(write!(f, "{{"));

        for (i, x) in self.iter().enumerate() {
            if i != 0 { try!(write!(f, ", ")); }
            try!(write!(f, "{}", *x));
        }

        write!(f, "}}")
    }
}

impl<T: Ord> Default for TreeSet<T> {
    #[inline]
    fn default() -> TreeSet<T> { TreeSet::new() }
}

impl<T: Ord> TreeSet<T> {
    /// Creates an empty `TreeSet`.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    /// let mut set: TreeSet<int> = TreeSet::new();
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn new() -> TreeSet<T> { TreeSet{map: TreeMap::new()} }

    /// Gets 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]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn iter<'a>(&'a self) -> SetItems<'a, T> {
        SetItems{iter: self.map.iter()}
    }

    /// Gets 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()}
    }

    /// 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.into_iter().collect();
    /// assert_eq!(v, vec![1, 2, 3, 4, 5]);
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn into_iter(self) -> MoveSetItems<T> {
        self.map.into_iter().map(|(value, _)| value)
    }

    /// Gets a lazy iterator pointing to the first value not less than `v` (greater or equal).
    /// If all elements in the set are less than `v` empty iterator is returned.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    /// let set: TreeSet<int> = [2, 4, 6, 8].iter().map(|&x| x).collect();
    ///
    /// assert_eq!(set.lower_bound(&4).next(), Some(&4));
    /// assert_eq!(set.lower_bound(&5).next(), Some(&6));
    /// assert_eq!(set.lower_bound(&10).next(), None);
    /// ```
    #[inline]
    pub fn lower_bound<'a>(&'a self, v: &T) -> SetItems<'a, T> {
        SetItems{iter: self.map.lower_bound(v)}
    }

    /// Gets a lazy iterator pointing to the first value greater than `v`.
    /// If all elements in the set are less than or equal to `v` an
    /// empty iterator is returned.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    /// let set: TreeSet<int> = [2, 4, 6, 8].iter().map(|&x| x).collect();
    ///
    /// assert_eq!(set.upper_bound(&4).next(), Some(&6));
    /// assert_eq!(set.upper_bound(&5).next(), Some(&6));
    /// assert_eq!(set.upper_bound(&10).next(), None);
    /// ```
    #[inline]
    pub fn upper_bound<'a>(&'a self, v: &T) -> SetItems<'a, T> {
        SetItems{iter: self.map.upper_bound(v)}
    }

    /// Visits 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());
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn difference<'a>(&'a self, other: &'a TreeSet<T>) -> DifferenceItems<'a, T> {
        DifferenceItems{a: self.iter().peekable(), b: other.iter().peekable()}
    }

    /// Visits 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());
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn symmetric_difference<'a>(&'a self, other: &'a TreeSet<T>)
        -> SymDifferenceItems<'a, T> {
        SymDifferenceItems{a: self.iter().peekable(), b: other.iter().peekable()}
    }

    /// Visits 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());
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn intersection<'a>(&'a self, other: &'a TreeSet<T>)
        -> IntersectionItems<'a, T> {
        IntersectionItems{a: self.iter().peekable(), b: other.iter().peekable()}
    }

    /// Visits the values representing the union, 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, 3, 4, 5 in ascending order.
    /// for x in a.union(&b) {
    ///     println!("{}", x);
    /// }
    ///
    /// let diff: TreeSet<int> = a.union(&b).map(|&x| x).collect();
    /// assert_eq!(diff, [1, 2, 3, 4, 5].iter().map(|&x| x).collect());
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn union<'a>(&'a self, other: &'a TreeSet<T>) -> UnionItems<'a, T> {
        UnionItems{a: self.iter().peekable(), b: other.iter().peekable()}
    }

    /// Return the number of elements in the set
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let mut v = TreeSet::new();
    /// assert_eq!(v.len(), 0);
    /// v.insert(1i);
    /// assert_eq!(v.len(), 1);
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn len(&self) -> uint { self.map.len() }

    /// Returns true if the set contains no elements
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let mut v = TreeSet::new();
    /// assert!(v.is_empty());
    /// v.insert(1i);
    /// assert!(!v.is_empty());
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn is_empty(&self) -> bool { self.len() == 0 }

    /// Clears the set, removing all values.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let mut v = TreeSet::new();
    /// v.insert(1i);
    /// v.clear();
    /// assert!(v.is_empty());
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn clear(&mut self) { self.map.clear() }

    /// Returns `true` if the set contains a value.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let set: TreeSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
    /// assert_eq!(set.contains(&1), true);
    /// assert_eq!(set.contains(&4), false);
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn contains(&self, value: &T) -> bool {
        self.map.contains_key(value)
    }

    /// Returns `true` if the set has no elements in common with `other`.
    /// This is equivalent to checking for an empty intersection.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let a: TreeSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
    /// let mut b: TreeSet<int> = TreeSet::new();
    ///
    /// assert_eq!(a.is_disjoint(&b), true);
    /// b.insert(4);
    /// assert_eq!(a.is_disjoint(&b), true);
    /// b.insert(1);
    /// assert_eq!(a.is_disjoint(&b), false);
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn is_disjoint(&self, other: &TreeSet<T>) -> bool {
        self.intersection(other).next().is_none()
    }

    /// Returns `true` if the set is a subset of another.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let sup: TreeSet<int> = [1i, 2, 3].iter().map(|&x| x).collect();
    /// let mut set: TreeSet<int> = TreeSet::new();
    ///
    /// assert_eq!(set.is_subset(&sup), true);
    /// set.insert(2);
    /// assert_eq!(set.is_subset(&sup), true);
    /// set.insert(4);
    /// assert_eq!(set.is_subset(&sup), false);
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn is_subset(&self, other: &TreeSet<T>) -> bool {
        let mut x = self.iter();
        let mut y = other.iter();
        let mut a = x.next();
        let mut b = y.next();
        while a.is_some() {
            if b.is_none() {
                return false;
            }

            let a1 = a.unwrap();
            let b1 = b.unwrap();

            match b1.cmp(a1) {
                Less => (),
                Greater => return false,
                Equal => a = x.next(),
            }

            b = y.next();
        }
        true
    }

    /// Returns `true` if the set is a superset of another.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::TreeSet;
    ///
    /// let sub: TreeSet<int> = [1i, 2].iter().map(|&x| x).collect();
    /// let mut set: TreeSet<int> = TreeSet::new();
    ///
    /// assert_eq!(set.is_superset(&sub), false);
    ///
    /// set.insert(0);
    /// set.insert(1);
    /// assert_eq!(set.is_superset(&sub), false);
    ///
    /// set.insert(2);
    /// assert_eq!(set.is_superset(&sub), true);
    /// ```
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn is_superset(&self, other: &TreeSet<T>) -> bool {
        other.is_subset(self)
    }

    /// Adds a value to the set. Returns `true` if the value was not already
    /// present in the set.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::BTreeSet;
    ///
    /// let mut set = BTreeSet::new();
    ///
    /// assert_eq!(set.insert(2i), true);
    /// assert_eq!(set.insert(2i), false);
    /// assert_eq!(set.len(), 1);
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn insert(&mut self, value: T) -> bool { self.map.insert(value, ()).is_none() }

    /// Removes a value from the set. Returns `true` if the value was
    /// present in the set.
    ///
    /// # Example
    ///
    /// ```
    /// use std::collections::BTreeSet;
    ///
    /// let mut set = BTreeSet::new();
    ///
    /// set.insert(2i);
    /// assert_eq!(set.remove(&2), true);
    /// assert_eq!(set.remove(&2), false);
    /// ```
    #[inline]
    #[unstable = "matches collection reform specification, waiting for dust to settle"]
    pub fn remove(&mut self, value: &T) -> bool { self.map.remove(value).is_some() }
}

/// A lazy forward iterator over a set.
pub struct SetItems<'a, T:'a> {
    iter: Entries<'a, T, ()>
}

/// A lazy backward iterator over a set.
pub struct RevSetItems<'a, T:'a> {
    iter: RevEntries<'a, T, ()>
}

/// A lazy forward iterator over a set that consumes the set while iterating.
pub type MoveSetItems<T> = iter::Map<'static, (T, ()), T, MoveEntries<T, ()>>;

/// A lazy iterator producing elements in the set difference (in-order).
pub struct DifferenceItems<'a, T:'a> {
    a: Peekable<&'a T, SetItems<'a, T>>,
    b: Peekable<&'a T, SetItems<'a, T>>,
}

/// A lazy iterator producing elements in the set symmetric difference (in-order).
pub struct SymDifferenceItems<'a, T:'a> {
    a: Peekable<&'a T, SetItems<'a, T>>,
    b: Peekable<&'a T, SetItems<'a, T>>,
}

/// A lazy iterator producing elements in the set intersection (in-order).
pub struct IntersectionItems<'a, T:'a> {
    a: Peekable<&'a T, SetItems<'a, T>>,
    b: Peekable<&'a T, SetItems<'a, T>>,
}

/// A lazy iterator producing elements in the set union (in-order).
pub struct UnionItems<'a, T:'a> {
    a: Peekable<&'a T, SetItems<'a, T>>,
    b: Peekable<&'a T, SetItems<'a, T>>,
}

/// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
fn cmp_opt<T: Ord>(x: Option<&T>, y: Option<&T>,
                        short: Ordering, long: Ordering) -> Ordering {
    match (x, y) {
        (None    , _       ) => short,
        (_       , None    ) => long,
        (Some(x1), Some(y1)) => x1.cmp(y1),
    }
}


impl<'a, T> Iterator<&'a T> for SetItems<'a, T> {
    #[inline]
    fn next(&mut self) -> Option<&'a T> {
        self.iter.next().map(|(value, _)| value)
    }
}

impl<'a, T> Iterator<&'a T> for RevSetItems<'a, T> {
    #[inline]
    fn next(&mut self) -> Option<&'a T> {
        self.iter.next().map(|(value, _)| value)
    }
}

impl<'a, T: Ord> Iterator<&'a T> for DifferenceItems<'a, T> {
    fn next(&mut self) -> Option<&'a T> {
        loop {
            match cmp_opt(self.a.peek(), self.b.peek(), Less, Less) {
                Less    => return self.a.next(),
                Equal   => { self.a.next(); self.b.next(); }
                Greater => { self.b.next(); }
            }
        }
    }
}

impl<'a, T: Ord> Iterator<&'a T> for SymDifferenceItems<'a, T> {
    fn next(&mut self) -> Option<&'a T> {
        loop {
            match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
                Less    => return self.a.next(),
                Equal   => { self.a.next(); self.b.next(); }
                Greater => return self.b.next(),
            }
        }
    }
}

impl<'a, T: Ord> Iterator<&'a T> for IntersectionItems<'a, T> {
    fn next(&mut self) -> Option<&'a T> {
        loop {
            let o_cmp = match (self.a.peek(), self.b.peek()) {
                (None    , _       ) => None,
                (_       , None    ) => None,
                (Some(a1), Some(b1)) => Some(a1.cmp(b1)),
            };
            match o_cmp {
                None          => return None,
                Some(Less)    => { self.a.next(); }
                Some(Equal)   => { self.b.next(); return self.a.next() }
                Some(Greater) => { self.b.next(); }
            }
        }
    }
}

impl<'a, T: Ord> Iterator<&'a T> for UnionItems<'a, T> {
    fn next(&mut self) -> Option<&'a T> {
        loop {
            match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
                Less    => return self.a.next(),
                Equal   => { self.b.next(); return self.a.next() }
                Greater => return self.b.next(),
            }
        }
    }
}

impl<T: Ord> FromIterator<T> for TreeSet<T> {
    fn from_iter<Iter: Iterator<T>>(iter: Iter) -> TreeSet<T> {
        let mut set = TreeSet::new();
        set.extend(iter);
        set
    }
}

impl<T: Ord> Extendable<T> for TreeSet<T> {
    #[inline]
    fn extend<Iter: Iterator<T>>(&mut self, mut iter: Iter) {
        for elem in iter {
            self.insert(elem);
        }
    }
}

impl<S: Writer, T: Ord + Hash<S>> Hash<S> for TreeSet<T> {
    fn hash(&self, state: &mut S) {
        for elt in self.iter() {
            elt.hash(state);
        }
    }
}

#[cfg(test)]
mod test {
    use std::prelude::*;
    use std::hash;

    use super::TreeSet;

    #[test]
    fn test_clear() {
        let mut s = TreeSet::new();
        s.clear();
        assert!(s.insert(5i));
        assert!(s.insert(12));
        assert!(s.insert(19));
        s.clear();
        assert!(!s.contains(&5));
        assert!(!s.contains(&12));
        assert!(!s.contains(&19));
        assert!(s.is_empty());
    }

    #[test]
    fn test_disjoint() {
        let mut xs = TreeSet::new();
        let mut ys = TreeSet::new();
        assert!(xs.is_disjoint(&ys));
        assert!(ys.is_disjoint(&xs));
        assert!(xs.insert(5i));
        assert!(ys.insert(11i));
        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 = TreeSet::new();
        assert!(a.insert(0i));
        assert!(a.insert(5));
        assert!(a.insert(11));
        assert!(a.insert(7));

        let mut b = TreeSet::new();
        assert!(b.insert(0i));
        assert!(b.insert(7));
        assert!(b.insert(19));
        assert!(b.insert(250));
        assert!(b.insert(11));
        assert!(b.insert(200));

        assert!(!a.is_subset(&b));
        assert!(!a.is_superset(&b));
        assert!(!b.is_subset(&a));
        assert!(!b.is_superset(&a));

        assert!(b.insert(5));

        assert!(a.is_subset(&b));
        assert!(!a.is_superset(&b));
        assert!(!b.is_subset(&a));
        assert!(b.is_superset(&a));
    }

    #[test]
    fn test_iterator() {
        let mut m = TreeSet::new();

        assert!(m.insert(3i));
        assert!(m.insert(0));
        assert!(m.insert(4));
        assert!(m.insert(2));
        assert!(m.insert(1));

        let mut n = 0;
        for x in m.iter() {
            assert_eq!(*x, n);
            n += 1
        }
    }

    #[test]
    fn test_rev_iter() {
        let mut m = TreeSet::new();

        assert!(m.insert(3i));
        assert!(m.insert(0));
        assert!(m.insert(4));
        assert!(m.insert(2));
        assert!(m.insert(1));

        let mut n = 4;
        for x in m.rev_iter() {
            assert_eq!(*x, n);
            n -= 1;
        }
    }

    #[test]
    fn test_move_iter() {
        let s: TreeSet<int> = range(0i, 5).collect();

        let mut n = 0;
        for x in s.into_iter() {
            assert_eq!(x, n);
            n += 1;
        }
    }

    #[test]
    fn test_move_iter_size_hint() {
        let s: TreeSet<int> = vec!(0i, 1).into_iter().collect();

        let mut it = s.into_iter();

        assert_eq!(it.size_hint(), (2, Some(2)));
        assert!(it.next() != None);

        assert_eq!(it.size_hint(), (1, Some(1)));
        assert!(it.next() != None);

        assert_eq!(it.size_hint(), (0, Some(0)));
        assert_eq!(it.next(), None);
    }

    #[test]
    fn test_clone_eq() {
      let mut m = TreeSet::new();

      m.insert(1i);
      m.insert(2);

      assert!(m.clone() == m);
    }

    #[test]
    fn test_hash() {
      let mut x = TreeSet::new();
      let mut y = TreeSet::new();

      x.insert(1i);
      x.insert(2);
      x.insert(3);

      y.insert(3i);
      y.insert(2);
      y.insert(1);

      assert!(hash::hash(&x) == hash::hash(&y));
    }

    fn check(a: &[int],
             b: &[int],
             expected: &[int],
             f: |&TreeSet<int>, &TreeSet<int>, f: |&int| -> bool| -> bool) {
        let mut set_a = TreeSet::new();
        let mut set_b = TreeSet::new();

        for x in a.iter() { assert!(set_a.insert(*x)) }
        for y in b.iter() { assert!(set_b.insert(*y)) }

        let mut i = 0;
        f(&set_a, &set_b, |x| {
            assert_eq!(*x, expected[i]);
            i += 1;
            true
        });
        assert_eq!(i, expected.len());
    }

    #[test]
    fn test_intersection() {
        fn check_intersection(a: &[int], b: &[int], expected: &[int]) {
            check(a, b, expected, |x, y, f| x.intersection(y).all(f))
        }

        check_intersection([], [], []);
        check_intersection([1, 2, 3], [], []);
        check_intersection([], [1, 2, 3], []);
        check_intersection([2], [1, 2, 3], [2]);
        check_intersection([1, 2, 3], [2], [2]);
        check_intersection([11, 1, 3, 77, 103, 5, -5],
                           [2, 11, 77, -9, -42, 5, 3],
                           [3, 5, 11, 77]);
    }

    #[test]
    fn test_difference() {
        fn check_difference(a: &[int], b: &[int], expected: &[int]) {
            check(a, b, expected, |x, y, f| x.difference(y).all(f))
        }

        check_difference([], [], []);
        check_difference([1, 12], [], [1, 12]);
        check_difference([], [1, 2, 3, 9], []);
        check_difference([1, 3, 5, 9, 11],
                         [3, 9],
                         [1, 5, 11]);
        check_difference([-5, 11, 22, 33, 40, 42],
                         [-12, -5, 14, 23, 34, 38, 39, 50],
                         [11, 22, 33, 40, 42]);
    }

    #[test]
    fn test_symmetric_difference() {
        fn check_symmetric_difference(a: &[int], b: &[int],
                                      expected: &[int]) {
            check(a, b, expected, |x, y, f| x.symmetric_difference(y).all(f))
        }

        check_symmetric_difference([], [], []);
        check_symmetric_difference([1, 2, 3], [2], [1, 3]);
        check_symmetric_difference([2], [1, 2, 3], [1, 3]);
        check_symmetric_difference([1, 3, 5, 9, 11],
                                   [-2, 3, 9, 14, 22],
                                   [-2, 1, 5, 11, 14, 22]);
    }

    #[test]
    fn test_union() {
        fn check_union(a: &[int], b: &[int],
                                      expected: &[int]) {
            check(a, b, expected, |x, y, f| x.union(y).all(f))
        }

        check_union([], [], []);
        check_union([1, 2, 3], [2], [1, 2, 3]);
        check_union([2], [1, 2, 3], [1, 2, 3]);
        check_union([1, 3, 5, 9, 11, 16, 19, 24],
                    [-2, 1, 5, 9, 13, 19],
                    [-2, 1, 3, 5, 9, 11, 13, 16, 19, 24]);
    }

    #[test]
    fn test_zip() {
        let mut x = TreeSet::new();
        x.insert(5u);
        x.insert(12u);
        x.insert(11u);

        let mut y = TreeSet::new();
        y.insert("foo");
        y.insert("bar");

        let x = x;
        let y = y;
        let mut z = x.iter().zip(y.iter());

        // FIXME: #5801: this needs a type hint to compile...
        let result: Option<(&uint, & &'static str)> = z.next();
        assert_eq!(result.unwrap(), (&5u, &("bar")));

        let result: Option<(&uint, & &'static str)> = z.next();
        assert_eq!(result.unwrap(), (&11u, &("foo")));

        let result: Option<(&uint, & &'static str)> = z.next();
        assert!(result.is_none());
    }

    #[test]
    fn test_from_iter() {
        let xs = [1i, 2, 3, 4, 5, 6, 7, 8, 9];

        let set: TreeSet<int> = xs.iter().map(|&x| x).collect();

        for x in xs.iter() {
            assert!(set.contains(x));
        }
    }

    #[test]
    fn test_show() {
        let mut set: TreeSet<int> = TreeSet::new();
        let empty: TreeSet<int> = TreeSet::new();

        set.insert(1);
        set.insert(2);

        let set_str = format!("{}", set);

        assert!(set_str == "{1, 2}".to_string());
        assert_eq!(format!("{}", empty), "{}".to_string());
    }
}