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::prelude::*;
  15
  16 use core::cmp::Ordering::{self, Less, Greater, Equal};
  17 use core::fmt::Debug;
  18 use core::fmt;
  19 use core::iter::{Peekable, Map, FromIterator};
  20 use core::ops::{BitOr, BitAnd, BitXor, Sub};
  21
  22 use borrow::Borrow;
  23 use btree_map::{BTreeMap, Keys};
  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 #[derive(Clone, Hash, PartialEq, Eq, Ord, PartialOrd)]
  37 #[stable(feature = "rust1", since = "1.0.0")]
  38 pub struct BTreeSet<T>{
  39     map: BTreeMap<T, ()>,
  40 }
  41
  42 /// An iterator over a BTreeSet's items.
  43 #[stable(feature = "rust1", since = "1.0.0")]
  44 pub struct Iter<'a, T: 'a> {
  45     iter: Keys<'a, T, ()>
  46 }
  47
  48 /// An owning iterator over a BTreeSet's items.
  49 #[stable(feature = "rust1", since = "1.0.0")]
  50 pub struct IntoIter<T> {
  51     iter: Map<::btree_map::IntoIter<T, ()>, fn((T, ())) -> T>
  52 }
  53
  54 /// An iterator over a sub-range of BTreeSet's items.
  55 pub struct Range<'a, T: 'a> {
  56     iter: Map<::btree_map::Range<'a, T, ()>, fn((&'a T, &'a ())) -> &'a T>
  57 }
  58
  59 /// A lazy iterator producing elements in the set difference (in-order).
  60 #[stable(feature = "rust1", since = "1.0.0")]
  61 pub struct Difference<'a, T:'a> {
  62     a: Peekable<Iter<'a, T>>,
  63     b: Peekable<Iter<'a, T>>,
  64 }
  65
  66 /// A lazy iterator producing elements in the set symmetric difference (in-order).
  67 #[stable(feature = "rust1", since = "1.0.0")]
  68 pub struct SymmetricDifference<'a, T:'a> {
  69     a: Peekable<Iter<'a, T>>,
  70     b: Peekable<Iter<'a, T>>,
  71 }
  72
  73 /// A lazy iterator producing elements in the set intersection (in-order).
  74 #[stable(feature = "rust1", since = "1.0.0")]
  75 pub struct Intersection<'a, T:'a> {
  76     a: Peekable<Iter<'a, T>>,
  77     b: Peekable<Iter<'a, T>>,
  78 }
  79
  80 /// A lazy iterator producing elements in the set union (in-order).
  81 #[stable(feature = "rust1", since = "1.0.0")]
  82 pub struct Union<'a, T:'a> {
  83     a: Peekable<Iter<'a, T>>,
  84     b: Peekable<Iter<'a, T>>,
  85 }
  86
  87 impl<T: Ord> BTreeSet<T> {
  88     /// Makes a new BTreeSet with a reasonable choice of B.
  89     ///
  90     /// # Examples
  91     ///
  92     /// ```
  93     /// use std::collections::BTreeSet;
  94     ///
  95     /// let mut set: BTreeSet<i32> = BTreeSet::new();
  96     /// ```
  97     #[stable(feature = "rust1", since = "1.0.0")]
  98     pub fn new() -> BTreeSet<T> {
  99         BTreeSet { map: BTreeMap::new() }
 100     }
 101
 102     /// Makes a new BTreeSet with the given B.
 103     ///
 104     /// B cannot be less than 2.
 105     #[unstable(feature = "btree_b",
 106                reason = "probably want this to be on the type, eventually")]
 107     pub fn with_b(b: usize) -> BTreeSet<T> {
 108         BTreeSet { map: BTreeMap::with_b(b) }
 109     }
 110 }
 111
 112 impl<T> BTreeSet<T> {
 113     /// Gets an iterator over the BTreeSet's contents.
 114     ///
 115     /// # Examples
 116     ///
 117     /// ```
 118     /// use std::collections::BTreeSet;
 119     ///
 120     /// let set: BTreeSet<usize> = [1, 2, 3, 4].iter().cloned().collect();
 121     ///
 122     /// for x in set.iter() {
 123     ///     println!("{}", x);
 124     /// }
 125     ///
 126     /// let v: Vec<_> = set.iter().cloned().collect();
 127     /// assert_eq!(v, [1, 2, 3, 4]);
 128     /// ```
 129     #[stable(feature = "rust1", since = "1.0.0")]
 130     pub fn iter(&self) -> Iter<T> {
 131         Iter { iter: self.map.keys() }
 132     }
 133 }
 134
 135 impl<T: Ord> BTreeSet<T> {
 136     /// Constructs a double-ended iterator over a sub-range of elements in the set, starting
 137     /// at min, and ending at max. If min is `Unbounded`, then it will be treated as "negative
 138     /// infinity", and if max is `Unbounded`, then it will be treated as "positive infinity".
 139     /// Thus range(Unbounded, Unbounded) will yield the whole collection.
 140     ///
 141     /// # Examples
 142     ///
 143     /// ```
 144     /// # #![feature(btree_range, collections_bound)]
 145     /// use std::collections::BTreeSet;
 146     /// use std::collections::Bound::{Included, Unbounded};
 147     ///
 148     /// let mut set = BTreeSet::new();
 149     /// set.insert(3);
 150     /// set.insert(5);
 151     /// set.insert(8);
 152     /// for &elem in set.range(Included(&4), Included(&8)) {
 153     ///     println!("{}", elem);
 154     /// }
 155     /// assert_eq!(Some(&5), set.range(Included(&4), Unbounded).next());
 156     /// ```
 157     #[unstable(feature = "btree_range",
 158                reason = "matches collection reform specification, waiting for dust to settle")]
 159     pub fn range<'a>(&'a self, min: Bound<&T>, max: Bound<&T>) -> Range<'a, T> {
 160         fn first<A, B>((a, _): (A, B)) -> A { a }
 161         let first: fn((&'a T, &'a ())) -> &'a T = first; // coerce to fn pointer
 162
 163         Range { iter: self.map.range(min, max).map(first) }
 164     }
 165 }
 166
 167 impl<T: Ord> BTreeSet<T> {
 168     /// Visits the values representing the difference, in ascending order.
 169     ///
 170     /// # Examples
 171     ///
 172     /// ```
 173     /// use std::collections::BTreeSet;
 174     ///
 175     /// let mut a = BTreeSet::new();
 176     /// a.insert(1);
 177     /// a.insert(2);
 178     ///
 179     /// let mut b = BTreeSet::new();
 180     /// b.insert(2);
 181     /// b.insert(3);
 182     ///
 183     /// let diff: Vec<_> = a.difference(&b).cloned().collect();
 184     /// assert_eq!(diff, [1]);
 185     /// ```
 186     #[stable(feature = "rust1", since = "1.0.0")]
 187     pub fn difference<'a>(&'a self, other: &'a BTreeSet<T>) -> Difference<'a, T> {
 188         Difference{a: self.iter().peekable(), b: other.iter().peekable()}
 189     }
 190
 191     /// Visits the values representing the symmetric difference, in ascending order.
 192     ///
 193     /// # Examples
 194     ///
 195     /// ```
 196     /// use std::collections::BTreeSet;
 197     ///
 198     /// let mut a = BTreeSet::new();
 199     /// a.insert(1);
 200     /// a.insert(2);
 201     ///
 202     /// let mut b = BTreeSet::new();
 203     /// b.insert(2);
 204     /// b.insert(3);
 205     ///
 206     /// let sym_diff: Vec<_> = a.symmetric_difference(&b).cloned().collect();
 207     /// assert_eq!(sym_diff, [1, 3]);
 208     /// ```
 209     #[stable(feature = "rust1", since = "1.0.0")]
 210     pub fn symmetric_difference<'a>(&'a self, other: &'a BTreeSet<T>)
 211         -> SymmetricDifference<'a, T> {
 212         SymmetricDifference{a: self.iter().peekable(), b: other.iter().peekable()}
 213     }
 214
 215     /// Visits the values representing the intersection, in ascending order.
 216     ///
 217     /// # Examples
 218     ///
 219     /// ```
 220     /// use std::collections::BTreeSet;
 221     ///
 222     /// let mut a = BTreeSet::new();
 223     /// a.insert(1);
 224     /// a.insert(2);
 225     ///
 226     /// let mut b = BTreeSet::new();
 227     /// b.insert(2);
 228     /// b.insert(3);
 229     ///
 230     /// let intersection: Vec<_> = a.intersection(&b).cloned().collect();
 231     /// assert_eq!(intersection, [2]);
 232     /// ```
 233     #[stable(feature = "rust1", since = "1.0.0")]
 234     pub fn intersection<'a>(&'a self, other: &'a BTreeSet<T>)
 235         -> Intersection<'a, T> {
 236         Intersection{a: self.iter().peekable(), b: other.iter().peekable()}
 237     }
 238
 239     /// Visits the values representing the union, in ascending order.
 240     ///
 241     /// # Examples
 242     ///
 243     /// ```
 244     /// use std::collections::BTreeSet;
 245     ///
 246     /// let mut a = BTreeSet::new();
 247     /// a.insert(1);
 248     ///
 249     /// let mut b = BTreeSet::new();
 250     /// b.insert(2);
 251     ///
 252     /// let union: Vec<_> = a.union(&b).cloned().collect();
 253     /// assert_eq!(union, [1, 2]);
 254     /// ```
 255     #[stable(feature = "rust1", since = "1.0.0")]
 256     pub fn union<'a>(&'a self, other: &'a BTreeSet<T>) -> Union<'a, T> {
 257         Union{a: self.iter().peekable(), b: other.iter().peekable()}
 258     }
 259
 260     /// Returns the number of elements in the set.
 261     ///
 262     /// # Examples
 263     ///
 264     /// ```
 265     /// use std::collections::BTreeSet;
 266     ///
 267     /// let mut v = BTreeSet::new();
 268     /// assert_eq!(v.len(), 0);
 269     /// v.insert(1);
 270     /// assert_eq!(v.len(), 1);
 271     /// ```
 272     #[stable(feature = "rust1", since = "1.0.0")]
 273     pub fn len(&self) -> usize { self.map.len() }
 274
 275     /// Returns true if the set contains no elements.
 276     ///
 277     /// # Examples
 278     ///
 279     /// ```
 280     /// use std::collections::BTreeSet;
 281     ///
 282     /// let mut v = BTreeSet::new();
 283     /// assert!(v.is_empty());
 284     /// v.insert(1);
 285     /// assert!(!v.is_empty());
 286     /// ```
 287     #[stable(feature = "rust1", since = "1.0.0")]
 288     pub fn is_empty(&self) -> bool { self.len() == 0 }
 289
 290     /// Clears the set, removing all values.
 291     ///
 292     /// # Examples
 293     ///
 294     /// ```
 295     /// use std::collections::BTreeSet;
 296     ///
 297     /// let mut v = BTreeSet::new();
 298     /// v.insert(1);
 299     /// v.clear();
 300     /// assert!(v.is_empty());
 301     /// ```
 302     #[stable(feature = "rust1", since = "1.0.0")]
 303     pub fn clear(&mut self) {
 304         self.map.clear()
 305     }
 306
 307     /// Returns `true` if the set contains a value.
 308     ///
 309     /// The value may be any borrowed form of the set's value type,
 310     /// but the ordering on the borrowed form *must* match the
 311     /// ordering on the value type.
 312     ///
 313     /// # Examples
 314     ///
 315     /// ```
 316     /// use std::collections::BTreeSet;
 317     ///
 318     /// let set: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
 319     /// assert_eq!(set.contains(&1), true);
 320     /// assert_eq!(set.contains(&4), false);
 321     /// ```
 322     #[stable(feature = "rust1", since = "1.0.0")]
 323     pub fn contains<Q: ?Sized>(&self, value: &Q) -> bool where T: Borrow<Q>, Q: Ord {
 324         self.map.contains_key(value)
 325     }
 326
 327     /// Returns `true` if the set has no elements in common with `other`.
 328     /// This is equivalent to checking for an empty intersection.
 329     ///
 330     /// # Examples
 331     ///
 332     /// ```
 333     /// use std::collections::BTreeSet;
 334     ///
 335     /// let a: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
 336     /// let mut b = BTreeSet::new();
 337     ///
 338     /// assert_eq!(a.is_disjoint(&b), true);
 339     /// b.insert(4);
 340     /// assert_eq!(a.is_disjoint(&b), true);
 341     /// b.insert(1);
 342     /// assert_eq!(a.is_disjoint(&b), false);
 343     /// ```
 344     #[stable(feature = "rust1", since = "1.0.0")]
 345     pub fn is_disjoint(&self, other: &BTreeSet<T>) -> bool {
 346         self.intersection(other).next().is_none()
 347     }
 348
 349     /// Returns `true` if the set is a subset of another.
 350     ///
 351     /// # Examples
 352     ///
 353     /// ```
 354     /// use std::collections::BTreeSet;
 355     ///
 356     /// let sup: BTreeSet<_> = [1, 2, 3].iter().cloned().collect();
 357     /// let mut set = BTreeSet::new();
 358     ///
 359     /// assert_eq!(set.is_subset(&sup), true);
 360     /// set.insert(2);
 361     /// assert_eq!(set.is_subset(&sup), true);
 362     /// set.insert(4);
 363     /// assert_eq!(set.is_subset(&sup), false);
 364     /// ```
 365     #[stable(feature = "rust1", since = "1.0.0")]
 366     pub fn is_subset(&self, other: &BTreeSet<T>) -> bool {
 367         // Stolen from TreeMap
 368         let mut x = self.iter();
 369         let mut y = other.iter();
 370         let mut a = x.next();
 371         let mut b = y.next();
 372         while a.is_some() {
 373             if b.is_none() {
 374                 return false;
 375             }
 376
 377             let a1 = a.unwrap();
 378             let b1 = b.unwrap();
 379
 380             match b1.cmp(a1) {
 381                 Less => (),
 382                 Greater => return false,
 383                 Equal => a = x.next(),
 384             }
 385
 386             b = y.next();
 387         }
 388         true
 389     }
 390
 391     /// Returns `true` if the set is a superset of another.
 392     ///
 393     /// # Examples
 394     ///
 395     /// ```
 396     /// use std::collections::BTreeSet;
 397     ///
 398     /// let sub: BTreeSet<_> = [1, 2].iter().cloned().collect();
 399     /// let mut set = BTreeSet::new();
 400     ///
 401     /// assert_eq!(set.is_superset(&sub), false);
 402     ///
 403     /// set.insert(0);
 404     /// set.insert(1);
 405     /// assert_eq!(set.is_superset(&sub), false);
 406     ///
 407     /// set.insert(2);
 408     /// assert_eq!(set.is_superset(&sub), true);
 409     /// ```
 410     #[stable(feature = "rust1", since = "1.0.0")]
 411     pub fn is_superset(&self, other: &BTreeSet<T>) -> bool {
 412         other.is_subset(self)
 413     }
 414
 415     /// Adds a value to the set. Returns `true` if the value was not already
 416     /// present in the set.
 417     ///
 418     /// # Examples
 419     ///
 420     /// ```
 421     /// use std::collections::BTreeSet;
 422     ///
 423     /// let mut set = BTreeSet::new();
 424     ///
 425     /// assert_eq!(set.insert(2), true);
 426     /// assert_eq!(set.insert(2), false);
 427     /// assert_eq!(set.len(), 1);
 428     /// ```
 429     #[stable(feature = "rust1", since = "1.0.0")]
 430     pub fn insert(&mut self, value: T) -> bool {
 431         self.map.insert(value, ()).is_none()
 432     }
 433
 434     /// Removes a value from the set. Returns `true` if the value was
 435     /// present in the set.
 436     ///
 437     /// The value may be any borrowed form of the set's value type,
 438     /// but the ordering on the borrowed form *must* match the
 439     /// ordering on the value type.
 440     ///
 441     /// # Examples
 442     ///
 443     /// ```
 444     /// use std::collections::BTreeSet;
 445     ///
 446     /// let mut set = BTreeSet::new();
 447     ///
 448     /// set.insert(2);
 449     /// assert_eq!(set.remove(&2), true);
 450     /// assert_eq!(set.remove(&2), false);
 451     /// ```
 452     #[stable(feature = "rust1", since = "1.0.0")]
 453     pub fn remove<Q: ?Sized>(&mut self, value: &Q) -> bool where T: Borrow<Q>, Q: Ord {
 454         self.map.remove(value).is_some()
 455     }
 456 }
 457
 458 #[stable(feature = "rust1", since = "1.0.0")]
 459 impl<T: Ord> FromIterator<T> for BTreeSet<T> {
 460     fn from_iter<I: IntoIterator<Item=T>>(iter: I) -> BTreeSet<T> {
 461         let mut set = BTreeSet::new();
 462         set.extend(iter);
 463         set
 464     }
 465 }
 466
 467 #[stable(feature = "rust1", since = "1.0.0")]
 468 impl<T> IntoIterator for BTreeSet<T> {
 469     type Item = T;
 470     type IntoIter = IntoIter<T>;
 471
 472     /// Gets an iterator for moving out the BtreeSet's contents.
 473     ///
 474     /// # Examples
 475     ///
 476     /// ```
 477     /// use std::collections::BTreeSet;
 478     ///
 479     /// let set: BTreeSet<usize> = [1, 2, 3, 4].iter().cloned().collect();
 480     ///
 481     /// let v: Vec<_> = set.into_iter().collect();
 482     /// assert_eq!(v, [1, 2, 3, 4]);
 483     /// ```
 484     fn into_iter(self) -> IntoIter<T> {
 485         fn first<A, B>((a, _): (A, B)) -> A { a }
 486         let first: fn((T, ())) -> T = first; // coerce to fn pointer
 487
 488         IntoIter { iter: self.map.into_iter().map(first) }
 489     }
 490 }
 491
 492 #[stable(feature = "rust1", since = "1.0.0")]
 493 impl<'a, T> IntoIterator for &'a BTreeSet<T> {
 494     type Item = &'a T;
 495     type IntoIter = Iter<'a, T>;
 496
 497     fn into_iter(self) -> Iter<'a, T> {
 498         self.iter()
 499     }
 500 }
 501
 502 #[stable(feature = "rust1", since = "1.0.0")]
 503 impl<T: Ord> Extend<T> for BTreeSet<T> {
 504     #[inline]
 505     fn extend<Iter: IntoIterator<Item=T>>(&mut self, iter: Iter) {
 506         for elem in iter {
 507             self.insert(elem);
 508         }
 509     }
 510 }
 511
 512 #[stable(feature = "extend_ref", since = "1.2.0")]
 513 impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BTreeSet<T> {
 514     fn extend<I: IntoIterator<Item=&'a T>>(&mut self, iter: I) {
 515         self.extend(iter.into_iter().cloned());
 516     }
 517 }
 518
 519 #[stable(feature = "rust1", since = "1.0.0")]
 520 impl<T: Ord> Default for BTreeSet<T> {
 521     #[stable(feature = "rust1", since = "1.0.0")]
 522     fn default() -> BTreeSet<T> {
 523         BTreeSet::new()
 524     }
 525 }
 526
 527 #[stable(feature = "rust1", since = "1.0.0")]
 528 impl<'a, 'b, T: Ord + Clone> Sub<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 529     type Output = BTreeSet<T>;
 530
 531     /// Returns the difference of `self` and `rhs` as a new `BTreeSet<T>`.
 532     ///
 533     /// # Examples
 534     ///
 535     /// ```
 536     /// use std::collections::BTreeSet;
 537     ///
 538     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 539     /// let b: BTreeSet<_> = vec![3, 4, 5].into_iter().collect();
 540     ///
 541     /// let result = &a - &b;
 542     /// let result_vec: Vec<_> = result.into_iter().collect();
 543     /// assert_eq!(result_vec, [1, 2]);
 544     /// ```
 545     fn sub(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 546         self.difference(rhs).cloned().collect()
 547     }
 548 }
 549
 550 #[stable(feature = "rust1", since = "1.0.0")]
 551 impl<'a, 'b, T: Ord + Clone> BitXor<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 552     type Output = BTreeSet<T>;
 553
 554     /// Returns the symmetric difference of `self` and `rhs` as a new `BTreeSet<T>`.
 555     ///
 556     /// # Examples
 557     ///
 558     /// ```
 559     /// use std::collections::BTreeSet;
 560     ///
 561     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 562     /// let b: BTreeSet<_> = vec![2, 3, 4].into_iter().collect();
 563     ///
 564     /// let result = &a ^ &b;
 565     /// let result_vec: Vec<_> = result.into_iter().collect();
 566     /// assert_eq!(result_vec, [1, 4]);
 567     /// ```
 568     fn bitxor(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 569         self.symmetric_difference(rhs).cloned().collect()
 570     }
 571 }
 572
 573 #[stable(feature = "rust1", since = "1.0.0")]
 574 impl<'a, 'b, T: Ord + Clone> BitAnd<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 575     type Output = BTreeSet<T>;
 576
 577     /// Returns the intersection of `self` and `rhs` as a new `BTreeSet<T>`.
 578     ///
 579     /// # Examples
 580     ///
 581     /// ```
 582     /// use std::collections::BTreeSet;
 583     ///
 584     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 585     /// let b: BTreeSet<_> = vec![2, 3, 4].into_iter().collect();
 586     ///
 587     /// let result = &a & &b;
 588     /// let result_vec: Vec<_> = result.into_iter().collect();
 589     /// assert_eq!(result_vec, [2, 3]);
 590     /// ```
 591     fn bitand(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 592         self.intersection(rhs).cloned().collect()
 593     }
 594 }
 595
 596 #[stable(feature = "rust1", since = "1.0.0")]
 597 impl<'a, 'b, T: Ord + Clone> BitOr<&'b BTreeSet<T>> for &'a BTreeSet<T> {
 598     type Output = BTreeSet<T>;
 599
 600     /// Returns the union of `self` and `rhs` as a new `BTreeSet<T>`.
 601     ///
 602     /// # Examples
 603     ///
 604     /// ```
 605     /// use std::collections::BTreeSet;
 606     ///
 607     /// let a: BTreeSet<_> = vec![1, 2, 3].into_iter().collect();
 608     /// let b: BTreeSet<_> = vec![3, 4, 5].into_iter().collect();
 609     ///
 610     /// let result = &a | &b;
 611     /// let result_vec: Vec<_> = result.into_iter().collect();
 612     /// assert_eq!(result_vec, [1, 2, 3, 4, 5]);
 613     /// ```
 614     fn bitor(self, rhs: &BTreeSet<T>) -> BTreeSet<T> {
 615         self.union(rhs).cloned().collect()
 616     }
 617 }
 618
 619 #[stable(feature = "rust1", since = "1.0.0")]
 620 impl<T: Debug> Debug for BTreeSet<T> {
 621     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 622         f.debug_set().entries(self.iter()).finish()
 623     }
 624 }
 625
 626 impl<'a, T> Clone for Iter<'a, T> {
 627     fn clone(&self) -> Iter<'a, T> { Iter { iter: self.iter.clone() } }
 628 }
 629 #[stable(feature = "rust1", since = "1.0.0")]
 630 impl<'a, T> Iterator for Iter<'a, T> {
 631     type Item = &'a T;
 632
 633     fn next(&mut self) -> Option<&'a T> { self.iter.next() }
 634     fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
 635 }
 636 #[stable(feature = "rust1", since = "1.0.0")]
 637 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
 638     fn next_back(&mut self) -> Option<&'a T> { self.iter.next_back() }
 639 }
 640 #[stable(feature = "rust1", since = "1.0.0")]
 641 impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
 642
 643
 644 #[stable(feature = "rust1", since = "1.0.0")]
 645 impl<T> Iterator for IntoIter<T> {
 646     type Item = T;
 647
 648     fn next(&mut self) -> Option<T> { self.iter.next() }
 649     fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
 650 }
 651 #[stable(feature = "rust1", since = "1.0.0")]
 652 impl<T> DoubleEndedIterator for IntoIter<T> {
 653     fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
 654 }
 655 #[stable(feature = "rust1", since = "1.0.0")]
 656 impl<T> ExactSizeIterator for IntoIter<T> {}
 657
 658
 659 impl<'a, T> Clone for Range<'a, T> {
 660     fn clone(&self) -> Range<'a, T> { Range { iter: self.iter.clone() } }
 661 }
 662 impl<'a, T> Iterator for Range<'a, T> {
 663     type Item = &'a T;
 664
 665     fn next(&mut self) -> Option<&'a T> { self.iter.next() }
 666 }
 667 impl<'a, T> DoubleEndedIterator for Range<'a, T> {
 668     fn next_back(&mut self) -> Option<&'a T> { self.iter.next_back() }
 669 }
 670
 671 /// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
 672 fn cmp_opt<T: Ord>(x: Option<&T>, y: Option<&T>,
 673                         short: Ordering, long: Ordering) -> Ordering {
 674     match (x, y) {
 675         (None    , _       ) => short,
 676         (_       , None    ) => long,
 677         (Some(x1), Some(y1)) => x1.cmp(y1),
 678     }
 679 }
 680
 681 impl<'a, T> Clone for Difference<'a, T> {
 682     fn clone(&self) -> Difference<'a, T> {
 683         Difference { a: self.a.clone(), b: self.b.clone() }
 684     }
 685 }
 686 #[stable(feature = "rust1", since = "1.0.0")]
 687 impl<'a, T: Ord> Iterator for Difference<'a, T> {
 688     type Item = &'a T;
 689
 690     fn next(&mut self) -> Option<&'a T> {
 691         loop {
 692             match cmp_opt(self.a.peek(), self.b.peek(), Less, Less) {
 693                 Less    => return self.a.next(),
 694                 Equal   => { self.a.next(); self.b.next(); }
 695                 Greater => { self.b.next(); }
 696             }
 697         }
 698     }
 699 }
 700
 701 impl<'a, T> Clone for SymmetricDifference<'a, T> {
 702     fn clone(&self) -> SymmetricDifference<'a, T> {
 703         SymmetricDifference { a: self.a.clone(), b: self.b.clone() }
 704     }
 705 }
 706 #[stable(feature = "rust1", since = "1.0.0")]
 707 impl<'a, T: Ord> Iterator for SymmetricDifference<'a, T> {
 708     type Item = &'a T;
 709
 710     fn next(&mut self) -> Option<&'a T> {
 711         loop {
 712             match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
 713                 Less    => return self.a.next(),
 714                 Equal   => { self.a.next(); self.b.next(); }
 715                 Greater => return self.b.next(),
 716             }
 717         }
 718     }
 719 }
 720
 721 impl<'a, T> Clone for Intersection<'a, T> {
 722     fn clone(&self) -> Intersection<'a, T> {
 723         Intersection { a: self.a.clone(), b: self.b.clone() }
 724     }
 725 }
 726 #[stable(feature = "rust1", since = "1.0.0")]
 727 impl<'a, T: Ord> Iterator for Intersection<'a, T> {
 728     type Item = &'a T;
 729
 730     fn next(&mut self) -> Option<&'a T> {
 731         loop {
 732             let o_cmp = match (self.a.peek(), self.b.peek()) {
 733                 (None    , _       ) => None,
 734                 (_       , None    ) => None,
 735                 (Some(a1), Some(b1)) => Some(a1.cmp(b1)),
 736             };
 737             match o_cmp {
 738                 None          => return None,
 739                 Some(Less)    => { self.a.next(); }
 740                 Some(Equal)   => { self.b.next(); return self.a.next() }
 741                 Some(Greater) => { self.b.next(); }
 742             }
 743         }
 744     }
 745 }
 746
 747 impl<'a, T> Clone for Union<'a, T> {
 748     fn clone(&self) -> Union<'a, T> {
 749         Union { a: self.a.clone(), b: self.b.clone() }
 750     }
 751 }
 752 #[stable(feature = "rust1", since = "1.0.0")]
 753 impl<'a, T: Ord> Iterator for Union<'a, T> {
 754     type Item = &'a T;
 755
 756     fn next(&mut self) -> Option<&'a T> {
 757         loop {
 758             match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
 759                 Less    => return self.a.next(),
 760                 Equal   => { self.b.next(); return self.a.next() }
 761                 Greater => return self.b.next(),
 762             }
 763         }
 764     }
 765 }