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 ///
 170 /// When this trait is `derive`d, it produces a lexicographic ordering.
 171 #[stable(feature = "rust1", since = "1.0.0")]
 172 pub trait Ord: Eq + PartialOrd<Self> {
 173     /// This method returns an `Ordering` between `self` and `other`.
 174     ///
 175     /// By convention, `self.cmp(&other)` returns the ordering matching the expression
 176     /// `self <operator> other` if true.
 177     ///
 178     /// # Examples
 179     ///
 180     /// ```
 181     /// use std::cmp::Ordering;
 182     ///
 183     /// assert_eq!(5.cmp(&10), Ordering::Less);
 184     /// assert_eq!(10.cmp(&5), Ordering::Greater);
 185     /// assert_eq!(5.cmp(&5), Ordering::Equal);
 186     /// ```
 187     #[stable(feature = "rust1", since = "1.0.0")]
 188     fn cmp(&self, other: &Self) -> Ordering;
 189 }
 190
 191 #[stable(feature = "rust1", since = "1.0.0")]
 192 impl Eq for Ordering {}
 193
 194 #[stable(feature = "rust1", since = "1.0.0")]
 195 impl Ord for Ordering {
 196     #[inline]
 197     #[stable(feature = "rust1", since = "1.0.0")]
 198     fn cmp(&self, other: &Ordering) -> Ordering {
 199         (*self as i32).cmp(&(*other as i32))
 200     }
 201 }
 202
 203 #[stable(feature = "rust1", since = "1.0.0")]
 204 impl PartialOrd for Ordering {
 205     #[inline]
 206     #[stable(feature = "rust1", since = "1.0.0")]
 207     fn partial_cmp(&self, other: &Ordering) -> Option<Ordering> {
 208         (*self as i32).partial_cmp(&(*other as i32))
 209     }
 210 }
 211
 212 /// Trait for values that can be compared for a sort-order.
 213 ///
 214 /// The comparison must satisfy, for all `a`, `b` and `c`:
 215 ///
 216 /// - antisymmetry: if `a < b` then `!(a > b)` and vice versa; and
 217 /// - transitivity: `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`.
 218 ///
 219 /// Note that these requirements mean that the trait itself must be implemented symmetrically and
 220 /// transitively: if `T: PartialOrd<U>` and `U: PartialOrd<V>` then `U: PartialOrd<T>` and `T:
 221 /// PartialOrd<V>`.
 222 ///
 223 /// PartialOrd only requires implementation of the `partial_cmp` method, with the others generated
 224 /// from default implementations.
 225 ///
 226 /// However it remains possible to implement the others separately for types which do not have a
 227 /// total order. For example, for floating point numbers, `NaN < 0 == false` and `NaN >= 0 ==
 228 /// false` (cf. IEEE 754-2008 section 5.11).
 229 #[lang = "ord"]
 230 #[stable(feature = "rust1", since = "1.0.0")]
 231 pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
 232     /// This method returns an ordering between `self` and `other` values if one exists.
 233     ///
 234     /// # Examples
 235     ///
 236     /// ```
 237     /// use std::cmp::Ordering;
 238     ///
 239     /// let result = 1.0.partial_cmp(&2.0);
 240     /// assert_eq!(result, Some(Ordering::Less));
 241     ///
 242     /// let result = 1.0.partial_cmp(&1.0);
 243     /// assert_eq!(result, Some(Ordering::Equal));
 244     ///
 245     /// let result = 2.0.partial_cmp(&1.0);
 246     /// assert_eq!(result, Some(Ordering::Greater));
 247     /// ```
 248     ///
 249     /// When comparison is impossible:
 250     ///
 251     /// ```
 252     /// let result = std::f64::NAN.partial_cmp(&1.0);
 253     /// assert_eq!(result, None);
 254     /// ```
 255     #[stable(feature = "rust1", since = "1.0.0")]
 256     fn partial_cmp(&self, other: &Rhs) -> Option<Ordering>;
 257
 258     /// This method tests less than (for `self` and `other`) and is used by the `<` operator.
 259     ///
 260     /// # Examples
 261     ///
 262     /// ```
 263     /// use std::cmp::Ordering;
 264     ///
 265     /// let result = 1.0 < 2.0;
 266     /// assert_eq!(result, true);
 267     ///
 268     /// let result = 2.0 < 1.0;
 269     /// assert_eq!(result, false);
 270     /// ```
 271     #[inline]
 272     #[stable(feature = "rust1", since = "1.0.0")]
 273     fn lt(&self, other: &Rhs) -> bool {
 274         match self.partial_cmp(other) {
 275             Some(Less) => true,
 276             _ => false,
 277         }
 278     }
 279
 280     /// This method tests less than or equal to (for `self` and `other`) and is used by the `<=`
 281     /// operator.
 282     ///
 283     /// # Examples
 284     ///
 285     /// ```
 286     /// let result = 1.0 <= 2.0;
 287     /// assert_eq!(result, true);
 288     ///
 289     /// let result = 2.0 <= 2.0;
 290     /// assert_eq!(result, true);
 291     /// ```
 292     #[inline]
 293     #[stable(feature = "rust1", since = "1.0.0")]
 294     fn le(&self, other: &Rhs) -> bool {
 295         match self.partial_cmp(other) {
 296             Some(Less) | Some(Equal) => true,
 297             _ => false,
 298         }
 299     }
 300
 301     /// This method tests greater than (for `self` and `other`) and is used by the `>` operator.
 302     ///
 303     /// # Examples
 304     ///
 305     /// ```
 306     /// let result = 1.0 > 2.0;
 307     /// assert_eq!(result, false);
 308     ///
 309     /// let result = 2.0 > 2.0;
 310     /// assert_eq!(result, false);
 311     /// ```
 312     #[inline]
 313     #[stable(feature = "rust1", since = "1.0.0")]
 314     fn gt(&self, other: &Rhs) -> bool {
 315         match self.partial_cmp(other) {
 316             Some(Greater) => true,
 317             _ => false,
 318         }
 319     }
 320
 321     /// This method tests greater than or equal to (for `self` and `other`) and is used by the `>=`
 322     /// operator.
 323     ///
 324     /// # Examples
 325     ///
 326     /// ```
 327     /// let result = 2.0 >= 1.0;
 328     /// assert_eq!(result, true);
 329     ///
 330     /// let result = 2.0 >= 2.0;
 331     /// assert_eq!(result, true);
 332     /// ```
 333     #[inline]
 334     #[stable(feature = "rust1", since = "1.0.0")]
 335     fn ge(&self, other: &Rhs) -> bool {
 336         match self.partial_cmp(other) {
 337             Some(Greater) | Some(Equal) => true,
 338             _ => false,
 339         }
 340     }
 341 }
 342
 343 /// Compare and return the minimum of two values.
 344 ///
 345 /// Returns the first argument if the comparison determines them to be equal.
 346 ///
 347 /// # Examples
 348 ///
 349 /// ```
 350 /// use std::cmp;
 351 ///
 352 /// assert_eq!(1, cmp::min(1, 2));
 353 /// assert_eq!(2, cmp::min(2, 2));
 354 /// ```
 355 #[inline]
 356 #[stable(feature = "rust1", since = "1.0.0")]
 357 pub fn min<T: Ord>(v1: T, v2: T) -> T {
 358     if v1 <= v2 { v1 } else { v2 }
 359 }
 360
 361 /// Compare and return the maximum of two values.
 362 ///
 363 /// Returns the second argument if the comparison determines them to be equal.
 364 ///
 365 /// # Examples
 366 ///
 367 /// ```
 368 /// use std::cmp;
 369 ///
 370 /// assert_eq!(2, cmp::max(1, 2));
 371 /// assert_eq!(2, cmp::max(2, 2));
 372 /// ```
 373 #[inline]
 374 #[stable(feature = "rust1", since = "1.0.0")]
 375 pub fn max<T: Ord>(v1: T, v2: T) -> T {
 376     if v2 >= v1 { v2 } else { v1 }
 377 }
 378
 379 /// Compare and return the minimum of two values if there is one.
 380 ///
 381 /// Returns the first argument if the comparison determines them to be equal.
 382 ///
 383 /// # Examples
 384 ///
 385 /// ```
 386 /// #![feature(cmp_partial)]
 387 ///
 388 /// use std::cmp;
 389 ///
 390 /// assert_eq!(Some(1), cmp::partial_min(1, 2));
 391 /// assert_eq!(Some(2), cmp::partial_min(2, 2));
 392 /// ```
 393 ///
 394 /// When comparison is impossible:
 395 ///
 396 /// ```
 397 /// #![feature(cmp_partial)]
 398 ///
 399 /// use std::cmp;
 400 ///
 401 /// let result = cmp::partial_min(std::f64::NAN, 1.0);
 402 /// assert_eq!(result, None);
 403 /// ```
 404 #[inline]
 405 #[unstable(feature = "cmp_partial")]
 406 #[deprecated(since = "1.3.0", reason = "has not proven itself worthwhile")]
 407 pub fn partial_min<T: PartialOrd>(v1: T, v2: T) -> Option<T> {
 408     match v1.partial_cmp(&v2) {
 409         Some(Less) | Some(Equal) => Some(v1),
 410         Some(Greater) => Some(v2),
 411         None => None
 412     }
 413 }
 414
 415 /// Compare and return the maximum of two values if there is one.
 416 ///
 417 /// Returns the second argument if the comparison determines them to be equal.
 418 ///
 419 /// # Examples
 420 ///
 421 /// ```
 422 /// #![feature(cmp_partial)]
 423 ///
 424 /// use std::cmp;
 425 ///
 426 /// assert_eq!(Some(2), cmp::partial_max(1, 2));
 427 /// assert_eq!(Some(2), cmp::partial_max(2, 2));
 428 /// ```
 429 ///
 430 /// When comparison is impossible:
 431 ///
 432 /// ```
 433 /// #![feature(cmp_partial)]
 434 ///
 435 /// use std::cmp;
 436 ///
 437 /// let result = cmp::partial_max(std::f64::NAN, 1.0);
 438 /// assert_eq!(result, None);
 439 /// ```
 440 #[inline]
 441 #[unstable(feature = "cmp_partial")]
 442 #[deprecated(since = "1.3.0", reason = "has not proven itself worthwhile")]
 443 pub fn partial_max<T: PartialOrd>(v1: T, v2: T) -> Option<T> {
 444     match v1.partial_cmp(&v2) {
 445         Some(Equal) | Some(Less) => Some(v2),
 446         Some(Greater) => Some(v1),
 447         None => None
 448     }
 449 }
 450
 451 // Implementation of PartialEq, Eq, PartialOrd and Ord for primitive types
 452 mod impls {
 453     use cmp::{PartialOrd, Ord, PartialEq, Eq, Ordering};
 454     use cmp::Ordering::{Less, Greater, Equal};
 455     use marker::Sized;
 456     use option::Option;
 457     use option::Option::{Some, None};
 458
 459     macro_rules! partial_eq_impl {
 460         ($($t:ty)*) => ($(
 461             #[stable(feature = "rust1", since = "1.0.0")]
 462             impl PartialEq for $t {
 463                 #[inline]
 464                 fn eq(&self, other: &$t) -> bool { (*self) == (*other) }
 465                 #[inline]
 466                 fn ne(&self, other: &$t) -> bool { (*self) != (*other) }
 467             }
 468         )*)
 469     }
 470
 471     #[stable(feature = "rust1", since = "1.0.0")]
 472     impl PartialEq for () {
 473         #[inline]
 474         fn eq(&self, _other: &()) -> bool { true }
 475         #[inline]
 476         fn ne(&self, _other: &()) -> bool { false }
 477     }
 478
 479     partial_eq_impl! {
 480         bool char usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64
 481     }
 482
 483     macro_rules! eq_impl {
 484         ($($t:ty)*) => ($(
 485             #[stable(feature = "rust1", since = "1.0.0")]
 486             impl Eq for $t {}
 487         )*)
 488     }
 489
 490     eq_impl! { () bool char usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 491
 492     macro_rules! partial_ord_impl {
 493         ($($t:ty)*) => ($(
 494             #[stable(feature = "rust1", since = "1.0.0")]
 495             impl PartialOrd for $t {
 496                 #[inline]
 497                 fn partial_cmp(&self, other: &$t) -> Option<Ordering> {
 498                     match (self <= other, self >= other) {
 499                         (false, false) => None,
 500                         (false, true) => Some(Greater),
 501                         (true, false) => Some(Less),
 502                         (true, true) => Some(Equal),
 503                     }
 504                 }
 505                 #[inline]
 506                 fn lt(&self, other: &$t) -> bool { (*self) < (*other) }
 507                 #[inline]
 508                 fn le(&self, other: &$t) -> bool { (*self) <= (*other) }
 509                 #[inline]
 510                 fn ge(&self, other: &$t) -> bool { (*self) >= (*other) }
 511                 #[inline]
 512                 fn gt(&self, other: &$t) -> bool { (*self) > (*other) }
 513             }
 514         )*)
 515     }
 516
 517     #[stable(feature = "rust1", since = "1.0.0")]
 518     impl PartialOrd for () {
 519         #[inline]
 520         fn partial_cmp(&self, _: &()) -> Option<Ordering> {
 521             Some(Equal)
 522         }
 523     }
 524
 525     #[stable(feature = "rust1", since = "1.0.0")]
 526     impl PartialOrd for bool {
 527         #[inline]
 528         fn partial_cmp(&self, other: &bool) -> Option<Ordering> {
 529             (*self as u8).partial_cmp(&(*other as u8))
 530         }
 531     }
 532
 533     partial_ord_impl! { char usize u8 u16 u32 u64 isize i8 i16 i32 i64 f32 f64 }
 534
 535     macro_rules! ord_impl {
 536         ($($t:ty)*) => ($(
 537             #[stable(feature = "rust1", since = "1.0.0")]
 538             impl Ord for $t {
 539                 #[inline]
 540                 fn cmp(&self, other: &$t) -> Ordering {
 541                     if *self < *other { Less }
 542                     else if *self > *other { Greater }
 543                     else { Equal }
 544                 }
 545             }
 546         )*)
 547     }
 548
 549     #[stable(feature = "rust1", since = "1.0.0")]
 550     impl Ord for () {
 551         #[inline]
 552         fn cmp(&self, _other: &()) -> Ordering { Equal }
 553     }
 554
 555     #[stable(feature = "rust1", since = "1.0.0")]
 556     impl Ord for bool {
 557         #[inline]
 558         fn cmp(&self, other: &bool) -> Ordering {
 559             (*self as u8).cmp(&(*other as u8))
 560         }
 561     }
 562
 563     ord_impl! { char usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 564
 565     // & pointers
 566
 567     #[stable(feature = "rust1", since = "1.0.0")]
 568     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a A where A: PartialEq<B> {
 569         #[inline]
 570         fn eq(&self, other: & &'b B) -> bool { PartialEq::eq(*self, *other) }
 571         #[inline]
 572         fn ne(&self, other: & &'b B) -> bool { PartialEq::ne(*self, *other) }
 573     }
 574     #[stable(feature = "rust1", since = "1.0.0")]
 575     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b B> for &'a A where A: PartialOrd<B> {
 576         #[inline]
 577         fn partial_cmp(&self, other: &&'b B) -> Option<Ordering> {
 578             PartialOrd::partial_cmp(*self, *other)
 579         }
 580         #[inline]
 581         fn lt(&self, other: & &'b B) -> bool { PartialOrd::lt(*self, *other) }
 582         #[inline]
 583         fn le(&self, other: & &'b B) -> bool { PartialOrd::le(*self, *other) }
 584         #[inline]
 585         fn ge(&self, other: & &'b B) -> bool { PartialOrd::ge(*self, *other) }
 586         #[inline]
 587         fn gt(&self, other: & &'b B) -> bool { PartialOrd::gt(*self, *other) }
 588     }
 589     #[stable(feature = "rust1", since = "1.0.0")]
 590     impl<'a, A: ?Sized> Ord for &'a A where A: Ord {
 591         #[inline]
 592         fn cmp(&self, other: & &'a A) -> Ordering { Ord::cmp(*self, *other) }
 593     }
 594     #[stable(feature = "rust1", since = "1.0.0")]
 595     impl<'a, A: ?Sized> Eq for &'a A where A: Eq {}
 596
 597     // &mut pointers
 598
 599     #[stable(feature = "rust1", since = "1.0.0")]
 600     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a mut A where A: PartialEq<B> {
 601         #[inline]
 602         fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
 603         #[inline]
 604         fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
 605     }
 606     #[stable(feature = "rust1", since = "1.0.0")]
 607     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b mut B> for &'a mut A where A: PartialOrd<B> {
 608         #[inline]
 609         fn partial_cmp(&self, other: &&'b mut B) -> Option<Ordering> {
 610             PartialOrd::partial_cmp(*self, *other)
 611         }
 612         #[inline]
 613         fn lt(&self, other: &&'b mut B) -> bool { PartialOrd::lt(*self, *other) }
 614         #[inline]
 615         fn le(&self, other: &&'b mut B) -> bool { PartialOrd::le(*self, *other) }
 616         #[inline]
 617         fn ge(&self, other: &&'b mut B) -> bool { PartialOrd::ge(*self, *other) }
 618         #[inline]
 619         fn gt(&self, other: &&'b mut B) -> bool { PartialOrd::gt(*self, *other) }
 620     }
 621     #[stable(feature = "rust1", since = "1.0.0")]
 622     impl<'a, A: ?Sized> Ord for &'a mut A where A: Ord {
 623         #[inline]
 624         fn cmp(&self, other: &&'a mut A) -> Ordering { Ord::cmp(*self, *other) }
 625     }
 626     #[stable(feature = "rust1", since = "1.0.0")]
 627     impl<'a, A: ?Sized> Eq for &'a mut A where A: Eq {}
 628
 629     #[stable(feature = "rust1", since = "1.0.0")]
 630     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a A where A: PartialEq<B> {
 631         #[inline]
 632         fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
 633         #[inline]
 634         fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
 635     }
 636
 637     #[stable(feature = "rust1", since = "1.0.0")]
 638     impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a mut A where A: PartialEq<B> {
 639         #[inline]
 640         fn eq(&self, other: &&'b B) -> bool { PartialEq::eq(*self, *other) }
 641         #[inline]
 642         fn ne(&self, other: &&'b B) -> bool { PartialEq::ne(*self, *other) }
 643     }
 644 }