src/libcollections/btree/set.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // This is pretty much entirely stolen from TreeSet, since BTreeMap has an identical interface
  12 // to TreeMap
  13
  14 use core::cmp::Ordering::{self, Less, Greater, Equal};
  15 use core::cmp::{min, max};
  16 use core::fmt::Debug;
  17 use core::fmt;
  18 use core::iter::{Peekable, FromIterator};
  19 use core::ops::{BitOr, BitAnd, BitXor, Sub};
  20
  21 use borrow::Borrow;
  22 use btree_map::{BTreeMap, Keys};
  23 use super::Recover;
  24 use Bound;
  25
  26 // FIXME(conventions): implement bounded iterators
  27
  28 /// A set based on a B-Tree.
  29 ///
  30 /// See [`BTreeMap`]'s documentation for a detailed discussion of this collection's performance
  31 /// benefits and drawbacks.
  32 ///
  33 /// It is a logic error for an item to be modified in such a way that the item's ordering relative
  34 /// to any other item, as determined by the [`Ord`] trait, changes while it is in the set. This is
  35 /// normally only possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
  36 ///
  37 /// [`BTreeMap`]: struct.BTreeMap.html
  38 /// [`Ord`]: ../../std/cmp/trait.Ord.html
  39 /// [`Cell`]: ../../std/cell/struct.Cell.html
  40 /// [`RefCell`]: ../../std/cell/struct.RefCell.html
  41 ///
  42 /// # Examples
  43 ///
  44 /// ```
  45 /// use std::collections::BTreeSet;
  46 ///
  47 /// // Type inference lets us omit an explicit type signature (which
  48 /// // would be `BTreeSet<&str>` in this example).
  49 /// let mut books = BTreeSet::new();
  50 ///
  51 /// // Add some books.
  52 /// books.insert("A Dance With Dragons");
  53 /// books.insert("To Kill a Mockingbird");
  54 /// books.insert("The Odyssey");
  55 /// books.insert("The Great Gatsby");
  56 ///
  57 /// // Check for a specific one.
  58 /// if !books.contains("The Winds of Winter") {
  59 ///     println!("We have {} books, but The Winds of Winter ain't one.",
  60 ///              books.len());
  61 /// }
  62 ///
  63 /// // Remove a book.
  64 /// books.remove("The Odyssey");
  65 ///
  66 /// // Iterate over everything.
  67 /// for book in &books {
  68 ///     println!("{}", book);
  69 /// }
  70 /// ```
  71 #[derive(Clone, Hash, PartialEq, Eq, Ord, PartialOrd)]
  72 #[stable(feature = "rust1", since = "1.0.0")]
  73 pub struct BTreeSet<T> {
  74     map: BTreeMap<T, ()>,
  75 }
  76
  77 /// An iterator over a BTreeSet's items.
  78 #[stable(feature = "rust1", since = "1.0.0")]
  79 pub struct Iter<'a, T: 'a> {
  80     iter: Keys<'a, T, ()>,
  81 }
  82
  83 /// An owning iterator over a BTreeSet's items.
  84 #[stable(feature = "rust1", since = "1.0.0")]
  85 pub struct IntoIter<T> {
  86     iter: ::btree_map::IntoIter<T, ()>,
  87 }
  88
  89 /// An iterator over a sub-range of BTreeSet's items.
  90 pub struct Range<'a, T: 'a> {
  91     iter: ::btree_map::Range<'a, T, ()>,
  92 }
  93
  94 /// A lazy iterator producing elements in the set difference (in-order).
  95 #[stable(feature = "rust1", since = "1.0.0")]
  96 pub struct Difference<'a, T: 'a> {
  97     a: Peekable<Iter<'a, T>>,
  98     b: Peekable<Iter<'a, T>>,
  99 }
 100
 101 /// A lazy iterator producing elements in the set symmetric difference (in-order).
 102 #[stable(feature = "rust1", since = "1.0.0")]
 103 pub struct SymmetricDifference<'a, T: 'a> {
 104     a: Peekable<Iter<'a, T>>,
 105     b: Peekable<Iter<'a, T>>,
 106 }
 107
 108 /// A lazy iterator producing elements in the set intersection (in-order).
 109 #[stable(feature = "rust1", since = "1.0.0")]
 110 pub struct Intersection<'a, T: 'a> {
 111     a: Peekable<Iter<'a, T>>,
 112     b: Peekable<Iter<'a, T>>,
 113 }
 114
 115 /// A lazy iterator producing elements in the set union (in-order).
 116 #[stable(feature = "rust1", since = "1.0.0")]
 117 pub struct Union<'a, T: 'a> {
 118     a: Peekable<Iter<'a, T>>,
 119     b: Peekable<Iter<'a, T>>,
 120 }
 121
 122 impl<T: Ord> BTreeSet<T> {
 123     /// Makes a new BTreeSet with a reasonable choice of B.
 124     ///
 125     /// # Examples
 126     ///
 127     /// ```
 128     /// # #![allow(unused_mut)]
 129     /// use std::collections::BTreeSet;
 130     ///
 131     /// let mut set: BTreeSet<i32> = BTreeSet::new();
 132     /// ```
 133     #[stable(feature = "rust1", since = "1.0.0")]
 134     pub fn new() -> BTreeSet<T> {
 135         BTreeSet { map: BTreeMap::new() }
 136     }
 137 }
 138
 139 impl<T> BTreeSet<T> {
 140     /// Gets an iterator over the BTreeSet's contents.
 141     ///
 142     /// # Examples
 143     ///
 144     /// ```
 145     /// use std::collections::BTreeSet;
 146     ///
 147     /// let set: BTreeSet<usize> = [1, 2, 3, 4].iter().cloned().collect();
 148     ///
 149     /// for x in set.iter() {
 150     ///     println!("{}", x);
 151     /// }
 152     ///
 153     /// let v: Vec<_> = set.iter().cloned().collect();
 154     /// assert_eq!(v, [1, 2, 3, 4]);
 155     /// ```
 156     #[stable(feature = "rust1", since = "1.0.0")]
 157     pub fn iter(&self) -> Iter<T> {
 158         Iter { iter: self.map.keys() }
 159     }
 160 }
 161
 162 impl<T: Ord> BTreeSet<T> {
 163     /// Constructs a double-ended iterator over a sub-range of elements in the set, starting
 164     /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
 165     /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
 166     /// Thus range(Unbounded, Unbounded) will yield the whole collection.
 167     ///
 168     /// # Examples
 169     ///
 170     /// ```
 171     /// #![feature(btree_range, collections_bound)]
 172     ///
 173     /// use std::collections::BTreeSet;
 174     /// use std::collections::Bound::{Included, Unbounded};
 175     ///
 176     /// let mut set = BTreeSet::new();
 177     /// set.insert(3);
 178     /// set.insert(5);
 179     /// set.insert(8);
 180     /// for &elem in set.range(Included(&4), Included(&8)) {
 181     ///     println!("{}", elem);
 182     /// }
 183     /// assert_eq!(Some(&5), set.range(Included(&4), Unbounded).next());
 184     /// ```
 185     #[unstable(feature = "btree_range",
 186                reason = "matches collection reform specification, waiting for dust to settle",
 187                issue = "27787")]
 188     pub fn range<'a, Min: ?Sized + Ord, Max: ?Sized + Ord>(&'a self,
 189                                                            min: Bound<&Min>,
 190                                                            max: Bound<&Max>)
 191                                                            -> Range<'a, T>
 192         where T: Borrow<Min> + Borrow<Max>
 193     {
 194         Range { iter: self.map.range(min, max) }
 195     }
 196 }
 197
 198 impl<T: Ord> BTreeSet<T> {
 199     /// Visits the values representing the difference, in ascending order.
 200     ///
 201     /// # Examples
 202     ///
 203     /// ```
 204     /// use std::collections::BTreeSet;
 205     ///
 206     /// let mut a = BTreeSet::new();
 207     /// a.insert(1);
 208     /// a.insert(2);
 209     ///
 210     /// let mut b = BTreeSet::new();
 211     /// b.insert(2);
 212     /// b.insert(3);
 213     ///
 214     /// let diff: Vec<_> = a.difference(&b).cloned().collect();
 215     /// assert_eq!(diff, [1]);
 216     /// ```
 217     #[stable(feature = "rust1", since = "1.0.0")]
 218     pub fn difference<'a>(&'a self, other: &'a BTreeSet<T>) -> Difference<'a, T> {
 219         Difference {
 220             a: self.iter().peekable(),
 221             b: other.iter().peekable(),
 222         }
 223     }
 224
 225     /// Visits the values representing the symmetric difference, in ascending order.
 226     ///
 227     /// # Examples
 228     ///
 229     /// ```
 230     /// use std::collections::BTreeSet;
 231     ///
 232     /// let mut a = BTreeSet::new();
 233     /// a.insert(1);
 234     /// a.insert(2);
 235     ///
 236     /// let mut b = BTreeSet::new();
 237     /// b.insert(2);
 238     /// b.insert(3);
 239     ///
 240     /// let sym_diff: Vec<_> = a.symmetric_difference(&b).cloned().collect();
 241     /// assert_eq!(sym_diff, [1, 3]);
 242     /// ```
 243     #[stable(feature = "rust1", since = "1.0.0")]
 244     pub fn symmetric_difference<'a>(&'a self,
 245                                     other: &'a BTreeSet<T>)
 246                                     -> SymmetricDifference<'a, T> {
 247         SymmetricDifference {
 248             a: self.iter().peekable(),
 249             b: other.iter().peekable(),
 250         }
 251     }
 252
 253     /// Visits the values representing the intersection, in ascending order.
 254     ///
 255     /// # Examples
 256     ///
 257     /// ```
 258     /// use std::collections::BTreeSet;
 259     ///
 260     /// let mut a = BTreeSet::new();
 261     /// a.insert(1);
 262     /// a.insert(2);
 263     ///
 264     /// let mut b = BTreeSet::new();
 265     /// b.insert(2);
 266     /// b.insert(3);
 267     ///
 268     /// let intersection: Vec<_> = a.intersection(&b).cloned().collect();
 269     /// assert_eq!(intersection, [2]);
 270     /// ```
 271     #[stable(feature = "rust1", since = "1.0.0")]
 272     pub fn intersection<'a>(&'a self, other: &'a BTreeSet<T>) -> Intersection<'a, T> {
 273         Intersection {
 274             a: self.iter().peekable(),
 275             b: other.iter().peekable(),
 276         }
 277     }
 278
 279     /// Visits the values representing the union, in ascending order.
 280     ///
 281     /// # Examples
 282     ///
 283     /// ```
 284     /// use std::collections::BTreeSet;
 285     ///
 286     /// let mut a = BTreeSet::new();
 287     /// a.insert(1);
 288     ///
 289     /// let mut b = BTreeSet::new();
 290     /// b.insert(2);
 291     ///
 292     /// let union: Vec<_> = a.union(&b).cloned().collect();
 293     /// assert_eq!(union, [1, 2]);
 294     /// ```
 295     #[stable(feature = "rust1", since = "1.0.0")]
 296     pub fn union<'a>(&'a self, other: &'a BTreeSet<T>) -> Union<'a, T> {
 297         Union {
 298             a: self.iter().peekable(),
 299             b: other.iter().peekable(),
 300         }
 301     }
 302
 303     /// Returns the number of elements in the set.
 304     ///
 305     /// # Examples
 306     ///
 307     /// ```
 308     /// use std::collections::BTreeSet;
 309     ///
 310     /// let mut v = BTreeSet::new();
 311     /// assert_eq!(v.len(), 0);
 312     /// v.insert(1);
 313     /// assert_eq!(v.len(), 1);
 314     /// ```
 315     #[stable(feature = "rust1", since = "1.0.0")]
 316     pub fn len(&self) -> usize {
 317         self.map.len()
 318     }
 319
 320     /// Returns true if the set contains no elements.
 321     ///
 322     /// # Examples
 323     ///
 324     /// ```
 325     /// use std::collections::BTreeSet;
 326     ///
 327     /// let mut v = BTreeSet::new();
 328     /// assert!(v.is_empty());
 329     /// v.insert(1);
 330     /// assert!(!v.is_empty());
 331     /// ```
 332     #[stable(feature = "rust1", since = "1.0.0")]
 333     pub fn is_empty(&self) -> bool {
 334         self.len() == 0
 335     }
 336
 337     /// Clears the set, removing all values.
 338     ///
 339     /// # Examples
 340     ///
 341     /// ```
 342     /// use std::collections::BTreeSet;
 343     ///
 344     /// let mut v = BTreeSet::new();
 345     /// v.insert(1);
 346     /// v.clear();
 347     /// assert!(v.is_empty());
 348     /// ```
 349     #[stable(feature = "rust1", since = "1.0.0")]
 350     pub fn clear(&mut self) {
 351         self.map.clear()
 352     }
 353
 354     /// Returns `true` if the set contains a value.
 355     ///
 356     /// The value may be any borrowed form of the set's value type,
 357     /// but the ordering on the borrowed form *must* match the
 358     /// ordering on the value type.
 359     ///
 360     /// # Examples
 361     ///
 362     /// ```
 363     /// use std::collections::BTreeSet;
 364     ///
 365     /// let set: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
 366     /// assert_eq!(set.contains(&1), true);
 367     /// assert_eq!(set.contains(&4), false);
 368     /// ```
 369     #[stable(feature = "rust1", since = "1.0.0")]
 370     pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool
 371         where T: Borrow<Q>,
 372               Q: Ord
 373     {
 374         self.map.contains_key(value)
 375     }
 376
 377     /// Returns a reference to the value in the set, if any, that is equal to the given value.
 378     ///
 379     /// The value may be any borrowed form of the set's value type,
 380     /// but the ordering on the borrowed form *must* match the
 381     /// ordering on the value type.
 382     #[stable(feature = "set_recovery", since = "1.9.0")]
 383     pub fn get<Q: ?Sized>(&self, value: &Q) -> Option<&T>
 384         where T: Borrow<Q>,
 385               Q: Ord
 386     {
 387         Recover::get(&self.map, value)
 388     }
 389
 390     /// Returns `true` if the set has no elements in common with `other`.
 391     /// This is equivalent to checking for an empty intersection.
 392     ///
 393     /// # Examples
 394     ///
 395     /// ```
 396     /// use std::collections::BTreeSet;
 397     ///
 398     /// let a: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
 399     /// let mut b = BTreeSet::new();
 400     ///
 401     /// assert_eq!(a.is_disjoint(&b), true);
 402     /// b.insert(4);
 403     /// assert_eq!(a.is_disjoint(&b), true);
 404     /// b.insert(1);
 405     /// assert_eq!(a.is_disjoint(&b), false);
 406     /// ```
 407     #[stable(feature = "rust1", since = "1.0.0")]
 408     pub fn is_disjoint(&self, other: &BTreeSet<T>) -> bool {
 409         self.intersection(other).next().is_none()
 410     }
 411
 412     /// Returns `true` if the set is a subset of another.
 413     ///
 414     /// # Examples
 415     ///
 416     /// ```
 417     /// use std::collections::BTreeSet;
 418     ///
 419     /// let sup: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
 420     /// let mut set = BTreeSet::new();
 421     ///
 422     /// assert_eq!(set.is_subset(&sup), true);
 423     /// set.insert(2);
 424     /// assert_eq!(set.is_subset(&sup), true);
 425     /// set.insert(4);
 426     /// assert_eq!(set.is_subset(&sup), false);
 427     /// ```
 428     #[stable(feature = "rust1", since = "1.0.0")]
 429     pub fn is_subset(&self, other: &BTreeSet<T>) -> bool {
 430         // Stolen from TreeMap
 431         let mut x = self.iter();
 432         let mut y = other.iter();
 433         let mut a = x.next();
 434         let mut b = y.next();
 435         while a.is_some() {
 436             if b.is_none() {
 437                 return false;
 438             }
 439
 440             let a1 = a.unwrap();
 441             let b1 = b.unwrap();
 442
 443             match b1.cmp(a1) {
 444                 Less => (),
 445                 Greater => return false,
 446                 Equal => a = x.next(),
 447             }
 448
 449             b = y.next();
 450         }
 451         true
 452     }
 453
 454     /// Returns `true` if the set is a superset of another.
 455     ///
 456     /// # Examples
 457     ///
 458     /// ```
 459     /// use std::collections::BTreeSet;
 460     ///
 461     /// let sub: BTreeSet<_> = [1, 2].iter().cloned().collect();
 462     /// let mut set = BTreeSet::new();
 463     ///
 464     /// assert_eq!(set.is_superset(&sub), false);
 465     ///
 466     /// set.insert(0);
 467     /// set.insert(1);
 468     /// assert_eq!(set.is_superset(&sub), false);
 469     ///
 470     /// set.insert(2);
 471     /// assert_eq!(set.is_superset(&sub), true);
 472     /// ```
 473     #[stable(feature = "rust1", since = "1.0.0")]
 474     pub fn is_superset(&self, other: &BTreeSet<T>) -> bool {
 475         other.is_subset(self)
 476     }
 477
 478     /// Adds a value to the set.
 479     ///
 480     /// If the set did not have a value present, `true` is returned.
 481     ///
 482     /// If the set did have this key present, `false` is returned, and the
 483     /// entry is not updated. See the [module-level documentation] for more.
 484     ///
 485     /// [module-level documentation]: index.html#insert-and-complex-keys
 486     ///
 487     /// # Examples
 488     ///
 489     /// ```
 490     /// use std::collections::BTreeSet;
 491     ///
 492     /// let mut set = BTreeSet::new();
 493     ///
 494     /// assert_eq!(set.insert(2), true);
 495     /// assert_eq!(set.insert(2), false);
 496     /// assert_eq!(set.len(), 1);
 497     /// ```
 498     #[stable(feature = "rust1", since = "1.0.0")]
 499     pub fn insert(&mut self, value: T) -> bool {
 500         self.map.insert(value, ()).is_none()
 501     }
 502
 503     /// Adds a value to the set, replacing the existing value, if any, that is equal to the given
 504     /// one. Returns the replaced value.
 505     #[stable(feature = "set_recovery", since = "1.9.0")]
 506     pub fn replace(&mut self, value: T) -> Option<T> {
 507         Recover::replace(&mut self.map, value)
 508     }
 509
 510     /// Removes a value from the set. Returns `true` if the value was
 511     /// present in the set.
 512     ///
 513     /// The value may be any borrowed form of the set's value type,
 514     /// but the ordering on the borrowed form *must* match the
 515     /// ordering on the value type.
 516     ///
 517     /// # Examples
 518     ///
 519     /// ```
 520     /// use std::collections::BTreeSet;
 521     ///
 522     /// let mut set = BTreeSet::new();
 523     ///
 524     /// set.insert(2);
 525     /// assert_eq!(set.remove(&2), true);
 526     /// assert_eq!(set.remove(&2), false);
 527     /// ```
 528     #[stable(feature = "rust1", since = "1.0.0")]
 529     pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool
 530         where T: Borrow<Q>,
 531               Q: Ord
 532     {
 533         self.map.remove(value).is_some()
 534     }
 535
 536     /// Removes and returns the value in the set, if any, that is equal to the given one.
 537     ///
 538     /// The value may be any borrowed form of the set's value type,
 539     /// but the ordering on the borrowed form *must* match the
 540     /// ordering on the value type.
 541     #[stable(feature = "set_recovery", since = "1.9.0")]
 542     pub fn take<Q: ?Sized>(&mut self, value: &Q) -> Option<T>
 543         where T: Borrow<Q>,
 544               Q: Ord
 545     {
 546         Recover::take(&mut self.map, value)
 547     }
 548 }
 549
 550 #[stable(feature = "rust1", since = "1.0.0")]
 551 impl<T: Ord> FromIterator<T> for BTreeSet<T> {
 552     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BTreeSet<T> {
 553         let mut set = BTreeSet::new();
 554         set.extend(iter);
 555         set
 556     }
 557 }
 558
 559 #[stable(feature = "rust1", since = "1.0.0")]
 560 impl<T> IntoIterator for BTreeSet<T> {
 561     type Item = T;
 562     type IntoIter = IntoIter<T>;
 563
 564     /// Gets an iterator for moving out the BtreeSet's contents.
 565     ///
 566     /// # Examples
 567     ///
 568     /// ```
 569     /// use std::collections::BTreeSet;
 570     ///
 571     /// let set: BTreeSet<usize> = [1, 2, 3, 4].iter().cloned().collect();
 572     ///
 573     /// let v: Vec<_> = set.into_iter().collect();
 574     /// assert_eq!(v, [1, 2, 3, 4]);
 575     /// ```
 576     fn into_iter(self) -> IntoIter<T> {
 577         IntoIter { iter: self.map.into_iter() }
 578     }
 579 }
 580
 581 #[stable(feature = "rust1", since = "1.0.0")]
 582 impl<'a, T> IntoIterator for &'a BTreeSet<T> {
 583     type Item = &'a T;
 584     type IntoIter = Iter<'a, T>;
 585
 586     fn into_iter(self) -> Iter<'a, T> {
 587         self.iter()
 588     }
 589 }
 590
 591 #[stable(feature = "rust1", since = "1.0.0")]
 592 impl<T: Ord> Extend<T> for BTreeSet<T> {
 593     #[inline]
 594     fn extend<Iter: IntoIterator<Item = T>>(&mut self, iter: Iter) {
 595         for elem in iter {
 596             self.insert(elem);
 597         }
 598     }
 599 }
 600
 601 #[stable(feature = "extend_ref", since = "1.2.0")]
 602 impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BTreeSet<T> {
 603     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
 604         self.extend(iter.into_iter().cloned());
 605     }
 606 }
 607
 608 #[stable(feature = "rust1", since = "1.0.0")]
 609 impl<T: Ord> Default for BTreeSet<T> {
 610     fn default() -> BTreeSet<T> {
 611         BTreeSet::new()
 612     }
 613 }
 614
 615 #[stable(feature = "rust1", since = "1.0.0")]
 616 impl<'a, 'b, T: Ord + Clone> Sub<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 617     type Output = BTreeSet<T>;
 618
 619     /// Returns the difference of `self` and `rhs` as a new `BTreeSet<T>`.
 620     ///
 621     /// # Examples
 622     ///
 623     /// ```
 624     /// use std::collections::BTreeSet;
 625     ///
 626     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 627     /// let b: BTreeSet<_> = vec![3, 4, 5].into_iter().collect();
 628     ///
 629     /// let result = &a - &b;
 630     /// let result_vec: Vec<_> = result.into_iter().collect();
 631     /// assert_eq!(result_vec, [1, 2]);
 632     /// ```
 633     fn sub(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 634         self.difference(rhs).cloned().collect()
 635     }
 636 }
 637
 638 #[stable(feature = "rust1", since = "1.0.0")]
 639 impl<'a, 'b, T: Ord + Clone> BitXor<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 640     type Output = BTreeSet<T>;
 641
 642     /// Returns the symmetric difference of `self` and `rhs` as a new `BTreeSet<T>`.
 643     ///
 644     /// # Examples
 645     ///
 646     /// ```
 647     /// use std::collections::BTreeSet;
 648     ///
 649     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 650     /// let b: BTreeSet<_> = vec![2, 3, 4].into_iter().collect();
 651     ///
 652     /// let result = &a ^ &b;
 653     /// let result_vec: Vec<_> = result.into_iter().collect();
 654     /// assert_eq!(result_vec, [1, 4]);
 655     /// ```
 656     fn bitxor(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 657         self.symmetric_difference(rhs).cloned().collect()
 658     }
 659 }
 660
 661 #[stable(feature = "rust1", since = "1.0.0")]
 662 impl<'a, 'b, T: Ord + Clone> BitAnd<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 663     type Output = BTreeSet<T>;
 664
 665     /// Returns the intersection of `self` and `rhs` as a new `BTreeSet<T>`.
 666     ///
 667     /// # Examples
 668     ///
 669     /// ```
 670     /// use std::collections::BTreeSet;
 671     ///
 672     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 673     /// let b: BTreeSet<_> = vec![2, 3, 4].into_iter().collect();
 674     ///
 675     /// let result = &a & &b;
 676     /// let result_vec: Vec<_> = result.into_iter().collect();
 677     /// assert_eq!(result_vec, [2, 3]);
 678     /// ```
 679     fn bitand(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 680         self.intersection(rhs).cloned().collect()
 681     }
 682 }
 683
 684 #[stable(feature = "rust1", since = "1.0.0")]
 685 impl<'a, 'b, T: Ord + Clone> BitOr<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 686     type Output = BTreeSet<T>;
 687
 688     /// Returns the union of `self` and `rhs` as a new `BTreeSet<T>`.
 689     ///
 690     /// # Examples
 691     ///
 692     /// ```
 693     /// use std::collections::BTreeSet;
 694     ///
 695     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 696     /// let b: BTreeSet<_> = vec![3, 4, 5].into_iter().collect();
 697     ///
 698     /// let result = &a | &b;
 699     /// let result_vec: Vec<_> = result.into_iter().collect();
 700     /// assert_eq!(result_vec, [1, 2, 3, 4, 5]);
 701     /// ```
 702     fn bitor(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 703         self.union(rhs).cloned().collect()
 704     }
 705 }
 706
 707 #[stable(feature = "rust1", since = "1.0.0")]
 708 impl<T: Debug> Debug for BTreeSet<T> {
 709     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 710         f.debug_set().entries(self.iter()).finish()
 711     }
 712 }
 713
 714 impl<'a, T> Clone for Iter<'a, T> {
 715     fn clone(&self) -> Iter<'a, T> {
 716         Iter { iter: self.iter.clone() }
 717     }
 718 }
 719 #[stable(feature = "rust1", since = "1.0.0")]
 720 impl<'a, T> Iterator for Iter<'a, T> {
 721     type Item = &'a T;
 722
 723     fn next(&mut self) -> Option<&'a T> {
 724         self.iter.next()
 725     }
 726     fn size_hint(&self) -> (usize, Option<usize>) {
 727         self.iter.size_hint()
 728     }
 729 }
 730 #[stable(feature = "rust1", since = "1.0.0")]
 731 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
 732     fn next_back(&mut self) -> Option<&'a T> {
 733         self.iter.next_back()
 734     }
 735 }
 736 #[stable(feature = "rust1", since = "1.0.0")]
 737 impl<'a, T> ExactSizeIterator for Iter<'a, T> {
 738     fn len(&self) -> usize { self.iter.len() }
 739 }
 740
 741
 742 #[stable(feature = "rust1", since = "1.0.0")]
 743 impl<T> Iterator for IntoIter<T> {
 744     type Item = T;
 745
 746     fn next(&mut self) -> Option<T> {
 747         self.iter.next().map(|(k, _)| k)
 748     }
 749     fn size_hint(&self) -> (usize, Option<usize>) {
 750         self.iter.size_hint()
 751     }
 752 }
 753 #[stable(feature = "rust1", since = "1.0.0")]
 754 impl<T> DoubleEndedIterator for IntoIter<T> {
 755     fn next_back(&mut self) -> Option<T> {
 756         self.iter.next_back().map(|(k, _)| k)
 757     }
 758 }
 759 #[stable(feature = "rust1", since = "1.0.0")]
 760 impl<T> ExactSizeIterator for IntoIter<T> {
 761     fn len(&self) -> usize { self.iter.len() }
 762 }
 763
 764
 765 impl<'a, T> Clone for Range<'a, T> {
 766     fn clone(&self) -> Range<'a, T> {
 767         Range { iter: self.iter.clone() }
 768     }
 769 }
 770 impl<'a, T> Iterator for Range<'a, T> {
 771     type Item = &'a T;
 772
 773     fn next(&mut self) -> Option<&'a T> {
 774         self.iter.next().map(|(k, _)| k)
 775     }
 776 }
 777 impl<'a, T> DoubleEndedIterator for Range<'a, T> {
 778     fn next_back(&mut self) -> Option<&'a T> {
 779         self.iter.next_back().map(|(k, _)| k)
 780     }
 781 }
 782
 783 /// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
 784 fn cmp_opt<T: Ord>(x: Option<&T>, y: Option<&T>, short: Ordering, long: Ordering) -> Ordering {
 785     match (x, y) {
 786         (None, _) => short,
 787         (_, None) => long,
 788         (Some(x1), Some(y1)) => x1.cmp(y1),
 789     }
 790 }
 791
 792 impl<'a, T> Clone for Difference<'a, T> {
 793     fn clone(&self) -> Difference<'a, T> {
 794         Difference {
 795             a: self.a.clone(),
 796             b: self.b.clone(),
 797         }
 798     }
 799 }
 800 #[stable(feature = "rust1", since = "1.0.0")]
 801 impl<'a, T: Ord> Iterator for Difference<'a, T> {
 802     type Item = &'a T;
 803
 804     fn next(&mut self) -> Option<&'a T> {
 805         loop {
 806             match cmp_opt(self.a.peek(), self.b.peek(), Less, Less) {
 807                 Less => return self.a.next(),
 808                 Equal => {
 809                     self.a.next();
 810                     self.b.next();
 811                 }
 812                 Greater => {
 813                     self.b.next();
 814                 }
 815             }
 816         }
 817     }
 818
 819     fn size_hint(&self) -> (usize, Option<usize>) {
 820         let a_len = self.a.len();
 821         let b_len = self.b.len();
 822         (a_len.saturating_sub(b_len), Some(a_len))
 823     }
 824 }
 825
 826 impl<'a, T> Clone for SymmetricDifference<'a, T> {
 827     fn clone(&self) -> SymmetricDifference<'a, T> {
 828         SymmetricDifference {
 829             a: self.a.clone(),
 830             b: self.b.clone(),
 831         }
 832     }
 833 }
 834 #[stable(feature = "rust1", since = "1.0.0")]
 835 impl<'a, T: Ord> Iterator for SymmetricDifference<'a, T> {
 836     type Item = &'a T;
 837
 838     fn next(&mut self) -> Option<&'a T> {
 839         loop {
 840             match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
 841                 Less => return self.a.next(),
 842                 Equal => {
 843                     self.a.next();
 844                     self.b.next();
 845                 }
 846                 Greater => return self.b.next(),
 847             }
 848         }
 849     }
 850
 851     fn size_hint(&self) -> (usize, Option<usize>) {
 852         (0, Some(self.a.len() + self.b.len()))
 853     }
 854 }
 855
 856 impl<'a, T> Clone for Intersection<'a, T> {
 857     fn clone(&self) -> Intersection<'a, T> {
 858         Intersection {
 859             a: self.a.clone(),
 860             b: self.b.clone(),
 861         }
 862     }
 863 }
 864 #[stable(feature = "rust1", since = "1.0.0")]
 865 impl<'a, T: Ord> Iterator for Intersection<'a, T> {
 866     type Item = &'a T;
 867
 868     fn next(&mut self) -> Option<&'a T> {
 869         loop {
 870             let o_cmp = match (self.a.peek(), self.b.peek()) {
 871                 (None, _) => None,
 872                 (_, None) => None,
 873                 (Some(a1), Some(b1)) => Some(a1.cmp(b1)),
 874             };
 875             match o_cmp {
 876                 None => return None,
 877                 Some(Less) => {
 878                     self.a.next();
 879                 }
 880                 Some(Equal) => {
 881                     self.b.next();
 882                     return self.a.next();
 883                 }
 884                 Some(Greater) => {
 885                     self.b.next();
 886                 }
 887             }
 888         }
 889     }
 890
 891     fn size_hint(&self) -> (usize, Option<usize>) {
 892         (0, Some(min(self.a.len(), self.b.len())))
 893     }
 894 }
 895
 896 impl<'a, T> Clone for Union<'a, T> {
 897     fn clone(&self) -> Union<'a, T> {
 898         Union {
 899             a: self.a.clone(),
 900             b: self.b.clone(),
 901         }
 902     }
 903 }
 904 #[stable(feature = "rust1", since = "1.0.0")]
 905 impl<'a, T: Ord> Iterator for Union<'a, T> {
 906     type Item = &'a T;
 907
 908     fn next(&mut self) -> Option<&'a T> {
 909         loop {
 910             match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
 911                 Less => return self.a.next(),
 912                 Equal => {
 913                     self.b.next();
 914                     return self.a.next();
 915                 }
 916                 Greater => return self.b.next(),
 917             }
 918         }
 919     }
 920
 921     fn size_hint(&self) -> (usize, Option<usize>) {
 922         let a_len = self.a.len();
 923         let b_len = self.b.len();
 924         (max(a_len, b_len), Some(a_len + b_len))
 925     }
 926 }