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.
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.
11 //! Defines the `PartialOrd` and `PartialEq` comparison traits.
13 //! This module defines both `PartialOrd` and `PartialEq` traits which are used by the
14 //! compiler to implement comparison operators. Rust programs may implement
15 //!`PartialOrd` to overload the `<`, `<=`, `>`, and `>=` operators, and may implement
16 //! `PartialEq` to overload the `==` and `!=` operators.
18 //! For example, to define a type with a customized definition for the PartialEq
19 //! operators, you could do the following:
22 //! use core::num::SignedInt;
25 //! struct SketchyNum {
29 //! // Our implementation of `PartialEq` to support `==` and `!=`.
30 //! impl PartialEq for SketchyNum {
31 //! // Our custom eq allows numbers which are near each other to be equal! :D
32 //! fn eq(&self, other: &SketchyNum) -> bool {
33 //! (self.num - other.num).abs() < 5
37 //! // Now these binary operators will work when applied!
38 //! assert!(SketchyNum {num: 37} == SketchyNum {num: 34});
39 //! assert!(SketchyNum {num: 25} != SketchyNum {num: 57});
44 use self::Ordering::*;
47 use option::Option::{mod, Some, None};
49 /// Trait for values that can be compared for equality and inequality.
51 /// This trait allows for partial equality, for types that do not have an
52 /// equivalence relation. For example, in floating point numbers `NaN != NaN`,
53 /// so floating point types implement `PartialEq` but not `Eq`.
55 /// PartialEq only requires the `eq` method to be implemented; `ne` is defined
56 /// in terms of it by default. Any manual implementation of `ne` *must* respect
57 /// the rule that `eq` is a strict inverse of `ne`; that is, `!(a == b)` if and
60 /// Eventually, this will be implemented by default for types that implement
63 #[unstable = "Definition may change slightly after trait reform"]
64 pub trait PartialEq<Sized? Rhs = Self> for Sized? {
65 /// This method tests for `self` and `other` values to be equal, and is used by `==`.
66 fn eq(&self, other: &Rhs) -> bool;
68 /// This method tests for `!=`.
70 fn ne(&self, other: &Rhs) -> bool { !self.eq(other) }
73 /// Trait for equality comparisons which are [equivalence relations](
74 /// https://en.wikipedia.org/wiki/Equivalence_relation).
76 /// This means, that in addition to `a == b` and `a != b` being strict
77 /// inverses, the equality must be (for all `a`, `b` and `c`):
79 /// - reflexive: `a == a`;
80 /// - symmetric: `a == b` implies `b == a`; and
81 /// - transitive: `a == b` and `b == c` implies `a == c`.
82 #[unstable = "Definition may change slightly after trait reform"]
83 pub trait Eq<Sized? Rhs = Self> for Sized?: PartialEq<Rhs> {
84 // FIXME #13101: this method is used solely by #[deriving] to
85 // assert that every component of a type implements #[deriving]
86 // itself, the current deriving infrastructure means doing this
87 // assertion without using a method on this trait is nearly
90 // This should never be implemented by hand.
93 fn assert_receiver_is_total_eq(&self) {}
96 /// An ordering is, e.g, a result of a comparison between two values.
97 #[deriving(Clone, Copy, PartialEq, Show)]
100 /// An ordering where a compared value is less [than another].
102 /// An ordering where a compared value is equal [to another].
104 /// An ordering where a compared value is greater [than another].
109 /// Reverse the `Ordering`, so that `Less` becomes `Greater` and
115 /// assert_eq!(Less.reverse(), Greater);
116 /// assert_eq!(Equal.reverse(), Equal);
117 /// assert_eq!(Greater.reverse(), Less);
120 /// let mut data: &mut [_] = &mut [2u, 10, 5, 8];
122 /// // sort the array from largest to smallest.
123 /// data.sort_by(|a, b| a.cmp(b).reverse());
125 /// let b: &mut [_] = &mut [10u, 8, 5, 2];
126 /// assert!(data == b);
130 pub fn reverse(self) -> Ordering {
132 // this compiles really nicely (to a single instruction);
133 // an explicit match has a pile of branches and
136 // NB. it is safe because of the explicit discriminants
138 ::mem::transmute::<_, Ordering>(-(self as i8))
143 /// Trait for types that form a [total order](
144 /// https://en.wikipedia.org/wiki/Total_order).
146 /// An order is a total order if it is (for all `a`, `b` and `c`):
148 /// - total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is
150 /// - transitive, `a < b` and `b < c` implies `a < c`. The same must hold for
151 /// both `==` and `>`.
152 #[unstable = "Definition may change slightly after trait reform"]
153 pub trait Ord<Sized? Rhs = Self> for Sized?: Eq<Rhs> + PartialOrd<Rhs> {
154 /// This method returns an ordering between `self` and `other` values.
156 /// By convention, `self.cmp(&other)` returns the ordering matching
157 /// the expression `self <operator> other` if true. For example:
160 /// assert_eq!( 5u.cmp(&10), Less); // because 5 < 10
161 /// assert_eq!(10u.cmp(&5), Greater); // because 10 > 5
162 /// assert_eq!( 5u.cmp(&5), Equal); // because 5 == 5
164 fn cmp(&self, other: &Rhs) -> Ordering;
167 #[unstable = "Trait is unstable."]
168 impl Eq for Ordering {}
170 #[unstable = "Trait is unstable."]
171 impl Ord for Ordering {
173 fn cmp(&self, other: &Ordering) -> Ordering {
174 (*self as int).cmp(&(*other as int))
178 #[unstable = "Trait is unstable."]
179 impl PartialOrd for Ordering {
181 fn partial_cmp(&self, other: &Ordering) -> Option<Ordering> {
182 (*self as int).partial_cmp(&(*other as int))
186 /// Trait for values that can be compared for a sort-order.
188 /// PartialOrd only requires implementation of the `partial_cmp` method,
189 /// with the others generated from default implementations.
191 /// However it remains possible to implement the others separately for types
192 /// which do not have a total order. For example, for floating point numbers,
193 /// `NaN < 0 == false` and `NaN >= 0 == false` (cf. IEEE 754-2008 section
196 #[unstable = "Definition may change slightly after trait reform"]
197 pub trait PartialOrd<Sized? Rhs = Self> for Sized?: PartialEq<Rhs> {
198 /// This method returns an ordering between `self` and `other` values
200 fn partial_cmp(&self, other: &Rhs) -> Option<Ordering>;
202 /// This method tests less than (for `self` and `other`) and is used by the `<` operator.
204 fn lt(&self, other: &Rhs) -> bool {
205 match self.partial_cmp(other) {
211 /// This method tests less than or equal to (`<=`).
213 fn le(&self, other: &Rhs) -> bool {
214 match self.partial_cmp(other) {
215 Some(Less) | Some(Equal) => true,
220 /// This method tests greater than (`>`).
222 fn gt(&self, other: &Rhs) -> bool {
223 match self.partial_cmp(other) {
224 Some(Greater) => true,
229 /// This method tests greater than or equal to (`>=`).
231 fn ge(&self, other: &Rhs) -> bool {
232 match self.partial_cmp(other) {
233 Some(Greater) | Some(Equal) => true,
239 /// The equivalence relation. Two values may be equivalent even if they are
240 /// of different types. The most common use case for this relation is
241 /// container types; e.g. it is often desirable to be able to use `&str`
242 /// values to look up entries in a container with `String` keys.
243 #[deprecated = "Use overloaded core::cmp::PartialEq"]
244 pub trait Equiv<Sized? T> for Sized? {
245 /// Implement this function to decide equivalent values.
246 fn equiv(&self, other: &T) -> bool;
249 /// Compare and return the minimum of two values.
252 pub fn min<T: Ord>(v1: T, v2: T) -> T {
253 if v1 < v2 { v1 } else { v2 }
256 /// Compare and return the maximum of two values.
259 pub fn max<T: Ord>(v1: T, v2: T) -> T {
260 if v1 > v2 { v1 } else { v2 }
263 /// Compare and return the minimum of two values if there is one.
265 /// Returns the first argument if the comparison determines them to be equal.
268 pub fn partial_min<T: PartialOrd>(v1: T, v2: T) -> Option<T> {
269 match v1.partial_cmp(&v2) {
270 Some(Less) | Some(Equal) => Some(v1),
271 Some(Greater) => Some(v2),
276 /// Compare and return the maximum of two values if there is one.
278 /// Returns the first argument if the comparison determines them to be equal.
281 pub fn partial_max<T: PartialOrd>(v1: T, v2: T) -> Option<T> {
282 match v1.partial_cmp(&v2) {
283 Some(Less) => Some(v2),
284 Some(Equal) | Some(Greater) => Some(v1),
289 // Implementation of PartialEq, Eq, PartialOrd and Ord for primitive types
291 use cmp::{PartialOrd, Ord, PartialEq, Eq, Ordering};
292 use cmp::Ordering::{Less, Greater, Equal};
295 use option::Option::{Some, None};
297 macro_rules! partial_eq_impl {
299 #[unstable = "Trait is unstable."]
300 impl PartialEq for $t {
302 fn eq(&self, other: &$t) -> bool { (*self) == (*other) }
304 fn ne(&self, other: &$t) -> bool { (*self) != (*other) }
309 #[unstable = "Trait is unstable."]
310 impl PartialEq for () {
312 fn eq(&self, _other: &()) -> bool { true }
314 fn ne(&self, _other: &()) -> bool { false }
318 bool char uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64
321 macro_rules! eq_impl {
323 #[unstable = "Trait is unstable."]
328 eq_impl! { () bool char uint u8 u16 u32 u64 int i8 i16 i32 i64 }
330 macro_rules! partial_ord_impl {
332 #[unstable = "Trait is unstable."]
333 impl PartialOrd for $t {
335 fn partial_cmp(&self, other: &$t) -> Option<Ordering> {
336 match (self <= other, self >= other) {
337 (false, false) => None,
338 (false, true) => Some(Greater),
339 (true, false) => Some(Less),
340 (true, true) => Some(Equal),
344 fn lt(&self, other: &$t) -> bool { (*self) < (*other) }
346 fn le(&self, other: &$t) -> bool { (*self) <= (*other) }
348 fn ge(&self, other: &$t) -> bool { (*self) >= (*other) }
350 fn gt(&self, other: &$t) -> bool { (*self) > (*other) }
355 #[unstable = "Trait is unstable."]
356 impl PartialOrd for () {
358 fn partial_cmp(&self, _: &()) -> Option<Ordering> {
363 #[unstable = "Trait is unstable."]
364 impl PartialOrd for bool {
366 fn partial_cmp(&self, other: &bool) -> Option<Ordering> {
367 (*self as u8).partial_cmp(&(*other as u8))
371 partial_ord_impl! { char uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64 }
373 macro_rules! ord_impl {
375 #[unstable = "Trait is unstable."]
378 fn cmp(&self, other: &$t) -> Ordering {
379 if *self < *other { Less }
380 else if *self > *other { Greater }
387 #[unstable = "Trait is unstable."]
390 fn cmp(&self, _other: &()) -> Ordering { Equal }
393 #[unstable = "Trait is unstable."]
396 fn cmp(&self, other: &bool) -> Ordering {
397 (*self as u8).cmp(&(*other as u8))
401 ord_impl! { char uint u8 u16 u32 u64 int i8 i16 i32 i64 }
405 #[unstable = "Trait is unstable."]
406 impl<'a, 'b, Sized? A, Sized? B> PartialEq<&'b B> for &'a A where A: PartialEq<B> {
408 fn eq(&self, other: & &'b B) -> bool { PartialEq::eq(*self, *other) }
410 fn ne(&self, other: & &'b B) -> bool { PartialEq::ne(*self, *other) }
412 #[unstable = "Trait is unstable."]
413 impl<'a, Sized? T: PartialOrd> PartialOrd for &'a T {
415 fn partial_cmp(&self, other: &&'a T) -> Option<Ordering> {
416 PartialOrd::partial_cmp(*self, *other)
419 fn lt(&self, other: & &'a T) -> bool { PartialOrd::lt(*self, *other) }
421 fn le(&self, other: & &'a T) -> bool { PartialOrd::le(*self, *other) }
423 fn ge(&self, other: & &'a T) -> bool { PartialOrd::ge(*self, *other) }
425 fn gt(&self, other: & &'a T) -> bool { PartialOrd::gt(*self, *other) }
427 #[unstable = "Trait is unstable."]
428 impl<'a, Sized? T: Ord> Ord for &'a T {
430 fn cmp(&self, other: & &'a T) -> Ordering { Ord::cmp(*self, *other) }
432 #[unstable = "Trait is unstable."]
433 impl<'a, Sized? T: Eq> Eq for &'a T {}
437 #[unstable = "Trait is unstable."]
438 impl<'a, 'b, Sized? A, Sized? B> PartialEq<&'b mut B> for &'a mut A where A: PartialEq<B> {
440 fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
442 fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
444 #[unstable = "Trait is unstable."]
445 impl<'a, Sized? T: PartialOrd> PartialOrd for &'a mut T {
447 fn partial_cmp(&self, other: &&'a mut T) -> Option<Ordering> {
448 PartialOrd::partial_cmp(*self, *other)
451 fn lt(&self, other: &&'a mut T) -> bool { PartialOrd::lt(*self, *other) }
453 fn le(&self, other: &&'a mut T) -> bool { PartialOrd::le(*self, *other) }
455 fn ge(&self, other: &&'a mut T) -> bool { PartialOrd::ge(*self, *other) }
457 fn gt(&self, other: &&'a mut T) -> bool { PartialOrd::gt(*self, *other) }
459 #[unstable = "Trait is unstable."]
460 impl<'a, Sized? T: Ord> Ord for &'a mut T {
462 fn cmp(&self, other: &&'a mut T) -> Ordering { Ord::cmp(*self, *other) }
464 #[unstable = "Trait is unstable."]
465 impl<'a, Sized? T: Eq> Eq for &'a mut T {}
467 impl<'a, 'b, Sized? A, Sized? B> PartialEq<&'b mut B> for &'a A where A: PartialEq<B> {
469 fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) }
471 fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) }
474 impl<'a, 'b, Sized? A, Sized? B> PartialEq<&'b B> for &'a mut A where A: PartialEq<B> {
476 fn eq(&self, other: &&'b B) -> bool { PartialEq::eq(*self, *other) }
478 fn ne(&self, other: &&'b B) -> bool { PartialEq::ne(*self, *other) }