src/libcore/cmp.rs

   1 // Copyright 2012-2014 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 //! Functionality for ordering and comparison.
  12 //!
  13 //! This module defines both `PartialOrd` and `PartialEq` traits which are used
  14 //! by the compiler to implement comparison operators. Rust programs may
  15 //! implement `PartialOrd` to overload the `<`, `<=`, `>`, and `>=` operators,
  16 //! and may implement `PartialEq` to overload the `==` and `!=` operators.
  17
  18 #![stable(feature = "rust1", since = "1.0.0")]
  19
  20 use self::Ordering::*;
  21
  22 use marker::Sized;
  23 use option::Option::{self, Some, None};
  24
  25 /// Trait for equality comparisons which are [partial equivalence
  26 /// relations](http://en.wikipedia.org/wiki/Partial_equivalence_relation).
  27 ///
  28 /// This trait allows for partial equality, for types that do not have a full
  29 /// equivalence relation.  For example, in floating point numbers `NaN != NaN`,
  30 /// so floating point types implement `PartialEq` but not `Eq`.
  31 ///
  32 /// Formally, the equality must be (for all `a`, `b` and `c`):
  33 ///
  34 /// - symmetric: `a == b` implies `b == a`; and
  35 /// - transitive: `a == b` and `b == c` implies `a == c`.
  36 ///
  37 /// Note that these requirements mean that the trait itself must be implemented
  38 /// symmetrically and transitively: if `T: PartialEq<U>` and `U: PartialEq<V>`
  39 /// then `U: PartialEq<T>` and `T: PartialEq<V>`.
  40 ///
  41 /// PartialEq only requires the `eq` method to be implemented; `ne` is defined
  42 /// in terms of it by default. Any manual implementation of `ne` *must* respect
  43 /// the rule that `eq` is a strict inverse of `ne`; that is, `!(a == b)` if and
  44 /// only if `a != b`.
  45 #[lang = "eq"]
  46 #[stable(feature = "rust1", since = "1.0.0")]
  47 pub trait PartialEq<Rhs: ?Sized = Self> {
  48     /// This method tests for `self` and `other` values to be equal, and is used
  49     /// by `==`.
  50     #[stable(feature = "rust1", since = "1.0.0")]
  51     fn eq(&self, other: &Rhs) -> bool;
  52
  53     /// This method tests for `!=`.
  54     #[inline]
  55     #[stable(feature = "rust1", since = "1.0.0")]
  56     fn ne(&self, other: &Rhs) -> bool { !self.eq(other) }
  57 }
  58
  59 /// Trait for equality comparisons which are [equivalence relations](
  60 /// https://en.wikipedia.org/wiki/Equivalence_relation).
  61 ///
  62 /// This means, that in addition to `a == b` and `a != b` being strict inverses, the equality must
  63 /// be (for all `a`, `b` and `c`):
  64 ///
  65 /// - reflexive: `a == a`;
  66 /// - symmetric: `a == b` implies `b == a`; and
  67 /// - transitive: `a == b` and `b == c` implies `a == c`.
  68 ///
  69 /// This property cannot be checked by the compiler, and therefore `Eq` implies
  70 /// `PartialEq`, and has no extra methods.
  71 #[stable(feature = "rust1", since = "1.0.0")]
  72 pub trait Eq: PartialEq<Self> {
  73     // FIXME #13101: this method is used solely by #[deriving] to
  74     // assert that every component of a type implements #[deriving]
  75     // itself, the current deriving infrastructure means doing this
  76     // assertion without using a method on this trait is nearly
  77     // impossible.
  78     //
  79     // This should never be implemented by hand.
  80     #[doc(hidden)]
  81     #[inline(always)]
  82     #[stable(feature = "rust1", since = "1.0.0")]
  83     fn assert_receiver_is_total_eq(&self) {}
  84 }
  85
  86 /// An `Ordering` is the result of a comparison between two values.
  87 ///
  88 /// # Examples
  89 ///
  90 /// ```
  91 /// use std::cmp::Ordering;
  92 ///
  93 /// let result = 1.cmp(&2);
  94 /// assert_eq!(Ordering::Less, result);
  95 ///
  96 /// let result = 1.cmp(&1);
  97 /// assert_eq!(Ordering::Equal, result);
  98 ///
  99 /// let result = 2.cmp(&1);
 100 /// assert_eq!(Ordering::Greater, result);
 101 /// ```
 102 #[derive(Clone, Copy, PartialEq, Debug)]
 103 #[stable(feature = "rust1", since = "1.0.0")]
 104 pub enum Ordering {
 105     /// An ordering where a compared value is less [than another].
 106     #[stable(feature = "rust1", since = "1.0.0")]
 107     Less = -1,
 108     /// An ordering where a compared value is equal [to another].
 109     #[stable(feature = "rust1", since = "1.0.0")]
 110     Equal = 0,
 111     /// An ordering where a compared value is greater [than another].
 112     #[stable(feature = "rust1", since = "1.0.0")]
 113     Greater = 1,
 114 }
 115
 116 impl Ordering {
 117     /// Reverse the `Ordering`.
 118     ///
 119     /// * `Less` becomes `Greater`.
 120     /// * `Greater` becomes `Less`.
 121     /// * `Equal` becomes `Equal`.
 122     ///
 123     /// # Examples
 124     ///
 125     /// Basic behavior:
 126     ///
 127     /// ```
 128     /// use std::cmp::Ordering;
 129     ///
 130     /// assert_eq!(Ordering::Less.reverse(), Ordering::Greater);
 131     /// assert_eq!(Ordering::Equal.reverse(), Ordering::Equal);
 132     /// assert_eq!(Ordering::Greater.reverse(), Ordering::Less);
 133     /// ```
 134     ///
 135     /// This method can be used to reverse a comparison:
 136     ///
 137     /// ```
 138     /// use std::cmp::Ordering;
 139     ///
 140     /// let mut data: &mut [_] = &mut [2, 10, 5, 8];
 141     ///
 142     /// // sort the array from largest to smallest.
 143     /// data.sort_by(|a, b| a.cmp(b).reverse());
 144     ///
 145     /// let b: &mut [_] = &mut [10, 8, 5, 2];
 146     /// assert!(data == b);
 147     /// ```
 148     #[inline]
 149     #[stable(feature = "rust1", since = "1.0.0")]
 150     pub fn reverse(self) -> Ordering {
 151         unsafe {
 152             // this compiles really nicely (to a single instruction);
 153             // an explicit match has a pile of branches and
 154             // comparisons.
 155             //
 156             // NB. it is safe because of the explicit discriminants
 157             // given above.
 158             ::mem::transmute::<_, Ordering>(-(self as i8))
 159         }
 160     }
 161 }
 162
 163 /// Trait for types that form a [total order](https://en.wikipedia.org/wiki/Total_order).
 164 ///
 165 /// An order is a total order if it is (for all `a`, `b` and `c`):
 166 ///
 167 /// - total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is true; and
 168 /// - transitive, `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`.
 169 #[stable(feature = "rust1", since = "1.0.0")]
 170 pub trait Ord: Eq + PartialOrd<Self> {
 171     /// This method returns an `Ordering` between `self` and `other`.
 172     ///
 173     /// By convention, `self.cmp(&other)` returns the ordering matching the expression
 174     /// `self <operator> other` if true.
 175     ///
 176     /// # Examples
 177     ///
 178     /// ```
 179     /// use std::cmp::Ordering;
 180     ///
 181     /// assert_eq!(5.cmp(&10), Ordering::Less);
 182     /// assert_eq!(10.cmp(&5), Ordering::Greater);
 183     /// assert_eq!(5.cmp(&5), Ordering::Equal);
 184     /// ```
 185     #[stable(feature = "rust1", since = "1.0.0")]
 186     fn cmp(&self, other: &Self) -> Ordering;
 187 }
 188
 189 #[stable(feature = "rust1", since = "1.0.0")]
 190 impl Eq for Ordering {}
 191
 192 #[stable(feature = "rust1", since = "1.0.0")]
 193 impl Ord for Ordering {
 194     #[inline]
 195     #[stable(feature = "rust1", since = "1.0.0")]
 196     fn cmp(&self, other: &Ordering) -> Ordering {
 197         (*self as i32).cmp(&(*other as i32))
 198     }
 199 }
 200
 201 #[stable(feature = "rust1", since = "1.0.0")]
 202 impl PartialOrd for Ordering {
 203     #[inline]
 204     #[stable(feature = "rust1", since = "1.0.0")]
 205     fn partial_cmp(&self, other: &Ordering) -> Option<Ordering> {
 206         (*self as i32).partial_cmp(&(*other as i32))
 207     }
 208 }
 209
 210 /// Trait for values that can be compared for a sort-order.
 211 ///
 212 /// The comparison must satisfy, for all `a`, `b` and `c`:
 213 ///
 214 /// - antisymmetry: if `a < b` then `!(a > b)` and vice versa; and
 215 /// - transitivity: `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`.
 216 ///
 217 /// Note that these requirements mean that the trait itself must be implemented symmetrically and
 218 /// transitively: if `T: PartialOrd<U>` and `U: PartialOrd<V>` then `U: PartialOrd<T>` and `T:
 219 /// PartialOrd<V>`.
 220 ///
 221 /// PartialOrd only requires implementation of the `partial_cmp` method, with the others generated
 222 /// from default implementations.
 223 ///
 224 /// However it remains possible to implement the others separately for types which do not have a
 225 /// total order. For example, for floating point numbers, `NaN < 0 == false` and `NaN >= 0 ==
 226 /// false` (cf. IEEE 754-2008 section 5.11).
 227 #[lang = "ord"]
 228 #[stable(feature = "rust1", since = "1.0.0")]
 229 pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
 230     /// This method returns an ordering between `self` and `other` values if one exists.
 231     ///
 232     /// # Examples
 233     ///
 234     /// ```
 235     /// use std::cmp::Ordering;
 236     ///
 237     /// let result = 1.0.partial_cmp(&2.0);
 238     /// assert_eq!(result, Some(Ordering::Less));
 239     ///
 240     /// let result = 1.0.partial_cmp(&1.0);
 241     /// assert_eq!(result, Some(Ordering::Equal));
 242     ///
 243     /// let result = 2.0.partial_cmp(&1.0);
 244     /// assert_eq!(result, Some(Ordering::Greater));
 245     /// ```
 246     ///
 247     /// When comparison is impossible:
 248     ///
 249     /// ```
 250     /// let result = std::f64::NAN.partial_cmp(&1.0);
 251     /// assert_eq!(result, None);
 252     /// ```
 253     #[stable(feature = "rust1", since = "1.0.0")]
 254     fn partial_cmp(&self, other: &Rhs) -> Option<Ordering>;
 255
 256     /// This method tests less than (for `self` and `other`) and is used by the `<` operator.
 257     ///
 258     /// # Examples
 259     ///
 260     /// ```
 261     /// use std::cmp::Ordering;
 262     ///
 263     /// let result = 1.0 < 2.0;
 264     /// assert_eq!(result, true);
 265     ///
 266     /// let result = 2.0 < 1.0;
 267     /// assert_eq!(result, false);
 268     /// ```
 269     #[inline]
 270     #[stable(feature = "rust1", since = "1.0.0")]
 271     fn lt(&self, other: &Rhs) -> bool {
 272         match self.partial_cmp(other) {
 273             Some(Less) => true,
 274             _ => false,
 275         }
 276     }
 277
 278     /// This method tests less than or equal to (for `self` and `other`) and is used by the `<=`
 279     /// operator.
 280     ///
 281     /// # Examples
 282     ///
 283     /// ```
 284     /// let result = 1.0 <= 2.0;
 285     /// assert_eq!(result, true);
 286     ///
 287     /// let result = 2.0 <= 2.0;
 288     /// assert_eq!(result, true);
 289     /// ```
 290     #[inline]
 291     #[stable(feature = "rust1", since = "1.0.0")]
 292     fn le(&self, other: &Rhs) -> bool {
 293         match self.partial_cmp(other) {
 294             Some(Less) | Some(Equal) => true,
 295             _ => false,
 296         }
 297     }
 298
 299     /// This method tests greater than (for `self` and `other`) and is used by the `>` operator.
 300     ///
 301     /// # Examples
 302     ///
 303     /// ```
 304     /// let result = 1.0 > 2.0;
 305     /// assert_eq!(result, false);
 306     ///
 307     /// let result = 2.0 > 2.0;
 308     /// assert_eq!(result, false);
 309     /// ```
 310     #[inline]
 311     #[stable(feature = "rust1", since = "1.0.0")]
 312     fn gt(&self, other: &Rhs) -> bool {
 313         match self.partial_cmp(other) {
 314             Some(Greater) => true,
 315             _ => false,
 316         }
 317     }
 318
 319     /// This method tests greater than or equal to (for `self` and `other`) and is used by the `>=`
 320     /// operator.
 321     ///
 322     /// # Examples
 323     ///
 324     /// ```
 325     /// let result = 2.0 >= 1.0;
 326     /// assert_eq!(result, true);
 327     ///
 328     /// let result = 2.0 >= 2.0;
 329     /// assert_eq!(result, true);
 330     /// ```
 331     #[inline]
 332     #[stable(feature = "rust1", since = "1.0.0")]
 333     fn ge(&self, other: &Rhs) -> bool {
 334         match self.partial_cmp(other) {
 335             Some(Greater) | Some(Equal) => true,
 336             _ => false,
 337         }
 338     }
 339 }
 340
 341 /// Compare and return the minimum of two values.
 342 ///
 343 /// Returns the first argument if the comparison determines them to be equal.
 344 ///
 345 /// # Examples
 346 ///
 347 /// ```
 348 /// use std::cmp;
 349 ///
 350 /// assert_eq!(1, cmp::min(1, 2));
 351 /// assert_eq!(2, cmp::min(2, 2));
 352 /// ```
 353 #[inline]
 354 #[stable(feature = "rust1", since = "1.0.0")]
 355 pub fn min<T: Ord>(v1: T, v2: T) -> T {
 356     if v1 <= v2 { v1 } else { v2 }
 357 }
 358
 359 /// Compare and return the maximum of two values.
 360 ///
 361 /// Returns the second argument if the comparison determines them to be equal.
 362 ///
 363 /// # Examples
 364 ///
 365 /// ```
 366 /// use std::cmp;
 367 ///
 368 /// assert_eq!(2, cmp::max(1, 2));
 369 /// assert_eq!(2, cmp::max(2, 2));
 370 /// ```
 371 #[inline]
 372 #[stable(feature = "rust1", since = "1.0.0")]
 373 pub fn max<T: Ord>(v1: T, v2: T) -> T {
 374     if v2 >= v1 { v2 } else { v1 }
 375 }
 376
 377 /// Compare and return the minimum of two values if there is one.
 378 ///
 379 /// Returns the first argument if the comparison determines them to be equal.
 380 ///
 381 /// # Examples
 382 ///
 383 /// ```
 384 /// # #![feature(cmp_partial)]
 385 /// use std::cmp;
 386 ///
 387 /// assert_eq!(Some(1), cmp::partial_min(1, 2));
 388 /// assert_eq!(Some(2), cmp::partial_min(2, 2));
 389 /// ```
 390 ///
 391 /// When comparison is impossible:
 392 ///
 393 /// ```
 394 /// # #![feature(cmp_partial)]
 395 /// use std::cmp;
 396 ///
 397 /// let result = cmp::partial_min(std::f64::NAN, 1.0);
 398 /// assert_eq!(result, None);
 399 /// ```
 400 #[inline]
 401 #[unstable(feature = "cmp_partial")]
 402 pub fn partial_min<T: PartialOrd>(v1: T, v2: T) -> Option<T> {
 403     match v1.partial_cmp(&v2) {
 404         Some(Less) | Some(Equal) => Some(v1),
 405         Some(Greater) => Some(v2),
 406         None => None
 407     }
 408 }
 409
 410 /// Compare and return the maximum of two values if there is one.
 411 ///
 412 /// Returns the second argument if the comparison determines them to be equal.
 413 ///
 414 /// # Examples
 415 ///
 416 /// ```
 417 /// # #![feature(cmp_partial)]
 418 /// use std::cmp;
 419 ///
 420 /// assert_eq!(Some(2), cmp::partial_max(1, 2));
 421 /// assert_eq!(Some(2), cmp::partial_max(2, 2));
 422 /// ```
 423 ///
 424 /// When comparison is impossible:
 425 ///
 426 /// ```
 427 /// # #![feature(cmp_partial)]
 428 /// use std::cmp;
 429 ///
 430 /// let result = cmp::partial_max(std::f64::NAN, 1.0);
 431 /// assert_eq!(result, None);
 432 /// ```
 433 #[inline]
 434 #[unstable(feature = "cmp_partial")]
 435 pub fn partial_max<T: PartialOrd>(v1: T, v2: T) -> Option<T> {
 436     match v1.partial_cmp(&v2) {
 437         Some(Equal) | Some(Less) => Some(v2),
 438         Some(Greater) => Some(v1),
 439         None => None
 440     }
 441 }
 442
 443 // Implementation of PartialEq, Eq, PartialOrd and Ord for primitive types
 444 mod impls {
 445     use cmp::{PartialOrd, Ord, PartialEq, Eq, Ordering};
 446     use cmp::Ordering::{Less, Greater, Equal};
 447     use marker::Sized;
 448     use option::Option;
 449     use option::Option::{Some, None};
 450
 451     macro_rules! partial_eq_impl {
 452         ($($t:ty)*) => ($(
 453             #[stable(feature = "rust1", since = "1.0.0")]
 454             impl PartialEq for $t {
 455                 #[inline]
 456                 fn eq(&self, other: &$t) -> bool { (*self) == (*other) }
 457                 #[inline]
 458                 fn ne(&self, other: &$t) -> bool { (*self) != (*other) }
 459             }
 460         )*)
 461     }
 462
 463     #[stable(feature = "rust1", since = "1.0.0")]
 464     impl PartialEq for () {
 465         #[inline]
 466         fn eq(&self, _other: &()) -> bool { true }
 467         #[inline]
 468         fn ne(&self, _other: &()) -> bool { false }
 469     }
 470
 471     partial_eq_impl! {
 472         bool char usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64
 473     }
 474
 475     macro_rules! eq_impl {
 476         ($($t:ty)*) => ($(
 477             #[stable(feature = "rust1", since = "1.0.0")]
 478             impl Eq for $t {}
 479         )*)
 480     }
 481
 482     eq_impl! { () bool char usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 483
 484     macro_rules! partial_ord_impl {
 485         ($($t:ty)*) => ($(
 486             #[stable(feature = "rust1", since = "1.0.0")]
 487             impl PartialOrd for $t {
 488                 #[inline]
 489                 fn partial_cmp(&self, other: &$t) -> Option<Ordering> {
 490                     match (self <= other, self >= other) {
 491                         (false, false) => None,
 492                         (false, true) => Some(Greater),
 493                         (true, false) => Some(Less),
 494                         (true, true) => Some(Equal),
 495                     }
 496                 }
 497                 #[inline]
 498                 fn lt(&self, other: &$t) -> bool { (*self) < (*other) }
 499                 #[inline]
 500                 fn le(&self, other: &$t) -> bool { (*self) <= (*other) }
 501                 #[inline]
 502                 fn ge(&self, other: &$t) -> bool { (*self) >= (*other) }
 503                 #[inline]
 504                 fn gt(&self, other: &$t) -> bool { (*self) > (*other) }
 505             }
 506         )*)
 507     }
 508
 509     #[stable(feature = "rust1", since = "1.0.0")]
 510     impl PartialOrd for () {
 511         #[inline]
 512         fn partial_cmp(&self, _: &()) -> Option<Ordering> {
 513             Some(Equal)
 514         }
 515     }
 516
 517     #[stable(feature = "rust1", since = "1.0.0")]
 518     impl PartialOrd for bool {
 519         #[inline]
 520         fn partial_cmp(&self, other: &bool) -> Option<Ordering> {
 521             (*self as u8).partial_cmp(&(*other as u8))
 522         }
 523     }
 524
 525     partial_ord_impl! { char usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64 }
 526
 527     macro_rules! ord_impl {
 528         ($($t:ty)*) => ($(
 529             #[stable(feature = "rust1", since = "1.0.0")]
 530             impl Ord for $t {
 531                 #[inline]
 532                 fn cmp(&self, other: &$t) -> Ordering {
 533                     if *self < *other { Less }
 534                     else if *self > *other { Greater }
 535                     else { Equal }
 536                 }
 537             }
 538         )*)
 539     }
 540
 541     #[stable(feature = "rust1", since = "1.0.0")]
 542     impl Ord for () {
 543         #[inline]
 544         fn cmp(&self, _other: &()) -> Ordering { Equal }
 545     }
 546
 547     #[stable(feature = "rust1", since = "1.0.0")]
 548     impl Ord for bool {
 549         #[inline]
 550         fn cmp(&self, other: &bool) -> Ordering {
 551             (*self as u8).cmp(&(*other as u8))
 552         }
 553     }
 554
 555     ord_impl! { char usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 556
 557     // & pointers
 558
 559     #[stable(feature = "rust1", since = "1.0.0")]
 560     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a A where A: PartialEq<B> {
 561         #[inline]
 562         fn eq(&self, other: & &'b B) -> bool { PartialEq::eq(*self, *other) }
 563         #[inline]
 564         fn ne(&self, other: & &'b B) -> bool { PartialEq::ne(*self, *other) }
 565     }
 566     #[stable(feature = "rust1", since = "1.0.0")]
 567     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b B> for &'a A where A: PartialOrd<B> {
 568         #[inline]
 569         fn partial_cmp(&self, other: &&'b B) -> Option<Ordering> {
 570             PartialOrd::partial_cmp(*self, *other)
 571         }
 572         #[inline]
 573         fn lt(&self, other: & &'b B) -> bool { PartialOrd::lt(*self, *other) }
 574         #[inline]
 575         fn le(&self, other: & &'b B) -> bool { PartialOrd::le(*self, *other) }
 576         #[inline]
 577         fn ge(&self, other: & &'b B) -> bool { PartialOrd::ge(*self, *other) }
 578         #[inline]
 579         fn gt(&self, other: & &'b B) -> bool { PartialOrd::gt(*self, *other) }
 580     }
 581     #[stable(feature = "rust1", since = "1.0.0")]
 582     impl<'a, A: ?Sized> Ord for &'a A where A: Ord {
 583         #[inline]
 584         fn cmp(&self, other: & &'a A) -> Ordering { Ord::cmp(*self, *other) }
 585     }
 586     #[stable(feature = "rust1", since = "1.0.0")]
 587     impl<'a, A: ?Sized> Eq for &'a A where A: Eq {}
 588
 589     // &mut pointers
 590
 591     #[stable(feature = "rust1", since = "1.0.0")]
 592     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a mut A where A: PartialEq<B> {
 593         #[inline]
 594         fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
 595         #[inline]
 596         fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
 597     }
 598     #[stable(feature = "rust1", since = "1.0.0")]
 599     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b mut B> for &'a mut A where A: PartialOrd<B> {
 600         #[inline]
 601         fn partial_cmp(&self, other: &&'b mut B) -> Option<Ordering> {
 602             PartialOrd::partial_cmp(*self, *other)
 603         }
 604         #[inline]
 605         fn lt(&self, other: &&'b mut B) -> bool { PartialOrd::lt(*self, *other) }
 606         #[inline]
 607         fn le(&self, other: &&'b mut B) -> bool { PartialOrd::le(*self, *other) }
 608         #[inline]
 609         fn ge(&self, other: &&'b mut B) -> bool { PartialOrd::ge(*self, *other) }
 610         #[inline]
 611         fn gt(&self, other: &&'b mut B) -> bool { PartialOrd::gt(*self, *other) }
 612     }
 613     #[stable(feature = "rust1", since = "1.0.0")]
 614     impl<'a, A: ?Sized> Ord for &'a mut A where A: Ord {
 615         #[inline]
 616         fn cmp(&self, other: &&'a mut A) -> Ordering { Ord::cmp(*self, *other) }
 617     }
 618     #[stable(feature = "rust1", since = "1.0.0")]
 619     impl<'a, A: ?Sized> Eq for &'a mut A where A: Eq {}
 620
 621     #[stable(feature = "rust1", since = "1.0.0")]
 622     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a A where A: PartialEq<B> {
 623         #[inline]
 624         fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
 625         #[inline]
 626         fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
 627     }
 628
 629     #[stable(feature = "rust1", since = "1.0.0")]
 630     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a mut A where A: PartialEq<B> {
 631         #[inline]
 632         fn eq(&self, other: &&'b B) -> bool { PartialEq::eq(*self, *other) }
 633         #[inline]
 634         fn ne(&self, other: &&'b B) -> bool { PartialEq::ne(*self, *other) }
 635     }
 636 }