| //! Functionality for ordering and comparison. |
| //! |
| //! This module contains various tools for ordering and comparing values. In |
| //! summary: |
| //! |
| //! * [`Eq`] and [`PartialEq`] are traits that allow you to define total and |
| //! partial equality between values, respectively. Implementing them overloads |
| //! the `==` and `!=` operators. |
| //! * [`Ord`] and [`PartialOrd`] are traits that allow you to define total and |
| //! partial orderings between values, respectively. Implementing them overloads |
| //! the `<`, `<=`, `>`, and `>=` operators. |
| //! * [`Ordering`][cmp::Ordering] is an enum returned by the |
| //! main functions of [`Ord`] and [`PartialOrd`], and describes an ordering. |
| //! * [`Reverse`][cmp::Reverse] is a struct that allows you to easily reverse |
| //! an ordering. |
| //! * [`max`][cmp::max] and [`min`][cmp::min] are functions that build off of |
| //! [`Ord`] and allow you to find the maximum or minimum of two values. |
| //! |
| //! For more details, see the respective documentation of each item in the list. |
| |
| #![stable(feature = "rust1", since = "1.0.0")] |
| |
| use self::Ordering::*; |
| |
| /// Trait for equality comparisons which are [partial equivalence |
| /// relations](http://en.wikipedia.org/wiki/Partial_equivalence_relation). |
| /// |
| /// This trait allows for partial equality, for types that do not have a full |
| /// equivalence relation. For example, in floating point numbers `NaN != NaN`, |
| /// so floating point types implement `PartialEq` but not `Eq`. |
| /// |
| /// Formally, the equality must be (for all `a`, `b` and `c`): |
| /// |
| /// - symmetric: `a == b` implies `b == a`; and |
| /// - transitive: `a == b` and `b == c` implies `a == c`. |
| /// |
| /// Note that these requirements mean that the trait itself must be implemented |
| /// symmetrically and transitively: if `T: PartialEq<U>` and `U: PartialEq<V>` |
| /// then `U: PartialEq<T>` and `T: PartialEq<V>`. |
| /// |
| /// ## Derivable |
| /// |
| /// This trait can be used with `#[derive]`. When `derive`d on structs, two |
| /// instances are equal if all fields are equal, and not equal if any fields |
| /// are not equal. When `derive`d on enums, each variant is equal to itself |
| /// and not equal to the other variants. |
| /// |
| /// ## How can I implement `PartialEq`? |
| /// |
| /// PartialEq only requires the `eq` method to be implemented; `ne` is defined |
| /// in terms of it by default. Any manual implementation of `ne` *must* respect |
| /// the rule that `eq` is a strict inverse of `ne`; that is, `!(a == b)` if and |
| /// only if `a != b`. |
| /// |
| /// Implementations of `PartialEq`, `PartialOrd`, and `Ord` *must* agree with |
| /// each other. It's easy to accidentally make them disagree by deriving some |
| /// of the traits and manually implementing others. |
| /// |
| /// An example implementation for a domain in which two books are considered |
| /// the same book if their ISBN matches, even if the formats differ: |
| /// |
| /// ``` |
| /// enum BookFormat { |
| /// Paperback, |
| /// Hardback, |
| /// Ebook, |
| /// } |
| /// |
| /// struct Book { |
| /// isbn: i32, |
| /// format: BookFormat, |
| /// } |
| /// |
| /// impl PartialEq for Book { |
| /// fn eq(&self, other: &Book) -> bool { |
| /// self.isbn == other.isbn |
| /// } |
| /// } |
| /// |
| /// let b1 = Book { isbn: 3, format: BookFormat::Paperback }; |
| /// let b2 = Book { isbn: 3, format: BookFormat::Ebook }; |
| /// let b3 = Book { isbn: 10, format: BookFormat::Paperback }; |
| /// |
| /// assert!(b1 == b2); |
| /// assert!(b1 != b3); |
| /// ``` |
| /// |
| /// ## How can I compare two different types? |
| /// |
| /// The type you can compare with is controlled by `PartialEq`'s type parameter. |
| /// For example, let's tweak our previous code a bit: |
| /// |
| /// ``` |
| /// enum BookFormat { |
| /// Paperback, |
| /// Hardback, |
| /// Ebook, |
| /// } |
| /// |
| /// struct Book { |
| /// isbn: i32, |
| /// format: BookFormat, |
| /// } |
| /// |
| /// impl PartialEq<BookFormat> for Book { |
| /// fn eq(&self, other: &BookFormat) -> bool { |
| /// match (&self.format, other) { |
| /// (BookFormat::Paperback, BookFormat::Paperback) => true, |
| /// (BookFormat::Hardback, BookFormat::Hardback) => true, |
| /// (BookFormat::Ebook, BookFormat::Ebook) => true, |
| /// (_, _) => false, |
| /// } |
| /// } |
| /// } |
| /// |
| /// let b1 = Book { isbn: 3, format: BookFormat::Paperback }; |
| /// |
| /// assert!(b1 == BookFormat::Paperback); |
| /// assert!(b1 != BookFormat::Ebook); |
| /// ``` |
| /// |
| /// By changing `impl PartialEq for Book` to `impl PartialEq<BookFormat> for Book`, |
| /// we've changed what type we can use on the right side of the `==` operator. |
| /// This lets us use it in the `assert!` statements at the bottom. |
| /// |
| /// You can also combine these implementations to let the `==` operator work with |
| /// two different types: |
| /// |
| /// ``` |
| /// enum BookFormat { |
| /// Paperback, |
| /// Hardback, |
| /// Ebook, |
| /// } |
| /// |
| /// struct Book { |
| /// isbn: i32, |
| /// format: BookFormat, |
| /// } |
| /// |
| /// impl PartialEq<BookFormat> for Book { |
| /// fn eq(&self, other: &BookFormat) -> bool { |
| /// match (&self.format, other) { |
| /// (&BookFormat::Paperback, &BookFormat::Paperback) => true, |
| /// (&BookFormat::Hardback, &BookFormat::Hardback) => true, |
| /// (&BookFormat::Ebook, &BookFormat::Ebook) => true, |
| /// (_, _) => false, |
| /// } |
| /// } |
| /// } |
| /// |
| /// impl PartialEq for Book { |
| /// fn eq(&self, other: &Book) -> bool { |
| /// self.isbn == other.isbn |
| /// } |
| /// } |
| /// |
| /// let b1 = Book { isbn: 3, format: BookFormat::Paperback }; |
| /// let b2 = Book { isbn: 3, format: BookFormat::Ebook }; |
| /// |
| /// assert!(b1 == BookFormat::Paperback); |
| /// assert!(b1 != BookFormat::Ebook); |
| /// assert!(b1 == b2); |
| /// ``` |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x: u32 = 0; |
| /// let y: u32 = 1; |
| /// |
| /// assert_eq!(x == y, false); |
| /// assert_eq!(x.eq(&y), false); |
| /// ``` |
| #[lang = "eq"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[doc(alias = "==")] |
| #[doc(alias = "!=")] |
| #[rustc_on_unimplemented( |
| message="can't compare `{Self}` with `{Rhs}`", |
| label="no implementation for `{Self} == {Rhs}`", |
| )] |
| pub trait PartialEq<Rhs: ?Sized = Self> { |
| /// This method tests for `self` and `other` values to be equal, and is used |
| /// by `==`. |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn eq(&self, other: &Rhs) -> bool; |
| |
| /// This method tests for `!=`. |
| #[inline] |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn ne(&self, other: &Rhs) -> bool { !self.eq(other) } |
| } |
| |
| /// Trait for equality comparisons which are [equivalence relations]( |
| /// https://en.wikipedia.org/wiki/Equivalence_relation). |
| /// |
| /// This means, that in addition to `a == b` and `a != b` being strict inverses, the equality must |
| /// be (for all `a`, `b` and `c`): |
| /// |
| /// - reflexive: `a == a`; |
| /// - symmetric: `a == b` implies `b == a`; and |
| /// - transitive: `a == b` and `b == c` implies `a == c`. |
| /// |
| /// This property cannot be checked by the compiler, and therefore `Eq` implies |
| /// `PartialEq`, and has no extra methods. |
| /// |
| /// ## Derivable |
| /// |
| /// This trait can be used with `#[derive]`. When `derive`d, because `Eq` has |
| /// no extra methods, it is only informing the compiler that this is an |
| /// equivalence relation rather than a partial equivalence relation. Note that |
| /// the `derive` strategy requires all fields are `Eq`, which isn't |
| /// always desired. |
| /// |
| /// ## How can I implement `Eq`? |
| /// |
| /// If you cannot use the `derive` strategy, specify that your type implements |
| /// `Eq`, which has no methods: |
| /// |
| /// ``` |
| /// enum BookFormat { Paperback, Hardback, Ebook } |
| /// struct Book { |
| /// isbn: i32, |
| /// format: BookFormat, |
| /// } |
| /// impl PartialEq for Book { |
| /// fn eq(&self, other: &Book) -> bool { |
| /// self.isbn == other.isbn |
| /// } |
| /// } |
| /// impl Eq for Book {} |
| /// ``` |
| #[doc(alias = "==")] |
| #[doc(alias = "!=")] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub trait Eq: PartialEq<Self> { |
| // this method is used solely by #[deriving] to assert |
| // that every component of a type implements #[deriving] |
| // itself, the current deriving infrastructure means doing this |
| // assertion without using a method on this trait is nearly |
| // impossible. |
| // |
| // This should never be implemented by hand. |
| #[doc(hidden)] |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn assert_receiver_is_total_eq(&self) {} |
| } |
| |
| // FIXME: this struct is used solely by #[derive] to |
| // assert that every component of a type implements Eq. |
| // |
| // This struct should never appear in user code. |
| #[doc(hidden)] |
| #[allow(missing_debug_implementations)] |
| #[unstable(feature = "derive_eq", |
| reason = "deriving hack, should not be public", |
| issue = "0")] |
| pub struct AssertParamIsEq<T: Eq + ?Sized> { _field: ::marker::PhantomData<T> } |
| |
| /// An `Ordering` is the result of a comparison between two values. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// let result = 1.cmp(&2); |
| /// assert_eq!(Ordering::Less, result); |
| /// |
| /// let result = 1.cmp(&1); |
| /// assert_eq!(Ordering::Equal, result); |
| /// |
| /// let result = 2.cmp(&1); |
| /// assert_eq!(Ordering::Greater, result); |
| /// ``` |
| #[derive(Clone, Copy, PartialEq, Debug, Hash)] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub enum Ordering { |
| /// An ordering where a compared value is less [than another]. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| Less = -1, |
| /// An ordering where a compared value is equal [to another]. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| Equal = 0, |
| /// An ordering where a compared value is greater [than another]. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| Greater = 1, |
| } |
| |
| impl Ordering { |
| /// Reverses the `Ordering`. |
| /// |
| /// * `Less` becomes `Greater`. |
| /// * `Greater` becomes `Less`. |
| /// * `Equal` becomes `Equal`. |
| /// |
| /// # Examples |
| /// |
| /// Basic behavior: |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// assert_eq!(Ordering::Less.reverse(), Ordering::Greater); |
| /// assert_eq!(Ordering::Equal.reverse(), Ordering::Equal); |
| /// assert_eq!(Ordering::Greater.reverse(), Ordering::Less); |
| /// ``` |
| /// |
| /// This method can be used to reverse a comparison: |
| /// |
| /// ``` |
| /// let mut data: &mut [_] = &mut [2, 10, 5, 8]; |
| /// |
| /// // sort the array from largest to smallest. |
| /// data.sort_by(|a, b| a.cmp(b).reverse()); |
| /// |
| /// let b: &mut [_] = &mut [10, 8, 5, 2]; |
| /// assert!(data == b); |
| /// ``` |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn reverse(self) -> Ordering { |
| match self { |
| Less => Greater, |
| Equal => Equal, |
| Greater => Less, |
| } |
| } |
| |
| /// Chains two orderings. |
| /// |
| /// Returns `self` when it's not `Equal`. Otherwise returns `other`. |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// let result = Ordering::Equal.then(Ordering::Less); |
| /// assert_eq!(result, Ordering::Less); |
| /// |
| /// let result = Ordering::Less.then(Ordering::Equal); |
| /// assert_eq!(result, Ordering::Less); |
| /// |
| /// let result = Ordering::Less.then(Ordering::Greater); |
| /// assert_eq!(result, Ordering::Less); |
| /// |
| /// let result = Ordering::Equal.then(Ordering::Equal); |
| /// assert_eq!(result, Ordering::Equal); |
| /// |
| /// let x: (i64, i64, i64) = (1, 2, 7); |
| /// let y: (i64, i64, i64) = (1, 5, 3); |
| /// let result = x.0.cmp(&y.0).then(x.1.cmp(&y.1)).then(x.2.cmp(&y.2)); |
| /// |
| /// assert_eq!(result, Ordering::Less); |
| /// ``` |
| #[inline] |
| #[stable(feature = "ordering_chaining", since = "1.17.0")] |
| pub fn then(self, other: Ordering) -> Ordering { |
| match self { |
| Equal => other, |
| _ => self, |
| } |
| } |
| |
| /// Chains the ordering with the given function. |
| /// |
| /// Returns `self` when it's not `Equal`. Otherwise calls `f` and returns |
| /// the result. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// let result = Ordering::Equal.then_with(|| Ordering::Less); |
| /// assert_eq!(result, Ordering::Less); |
| /// |
| /// let result = Ordering::Less.then_with(|| Ordering::Equal); |
| /// assert_eq!(result, Ordering::Less); |
| /// |
| /// let result = Ordering::Less.then_with(|| Ordering::Greater); |
| /// assert_eq!(result, Ordering::Less); |
| /// |
| /// let result = Ordering::Equal.then_with(|| Ordering::Equal); |
| /// assert_eq!(result, Ordering::Equal); |
| /// |
| /// let x: (i64, i64, i64) = (1, 2, 7); |
| /// let y: (i64, i64, i64) = (1, 5, 3); |
| /// let result = x.0.cmp(&y.0).then_with(|| x.1.cmp(&y.1)).then_with(|| x.2.cmp(&y.2)); |
| /// |
| /// assert_eq!(result, Ordering::Less); |
| /// ``` |
| #[inline] |
| #[stable(feature = "ordering_chaining", since = "1.17.0")] |
| pub fn then_with<F: FnOnce() -> Ordering>(self, f: F) -> Ordering { |
| match self { |
| Equal => f(), |
| _ => self, |
| } |
| } |
| } |
| |
| /// A helper struct for reverse ordering. |
| /// |
| /// This struct is a helper to be used with functions like `Vec::sort_by_key` and |
| /// can be used to reverse order a part of a key. |
| /// |
| /// Example usage: |
| /// |
| /// ``` |
| /// use std::cmp::Reverse; |
| /// |
| /// let mut v = vec![1, 2, 3, 4, 5, 6]; |
| /// v.sort_by_key(|&num| (num > 3, Reverse(num))); |
| /// assert_eq!(v, vec![3, 2, 1, 6, 5, 4]); |
| /// ``` |
| #[derive(PartialEq, Eq, Debug, Copy, Clone, Default, Hash)] |
| #[stable(feature = "reverse_cmp_key", since = "1.19.0")] |
| pub struct Reverse<T>(#[stable(feature = "reverse_cmp_key", since = "1.19.0")] pub T); |
| |
| #[stable(feature = "reverse_cmp_key", since = "1.19.0")] |
| impl<T: PartialOrd> PartialOrd for Reverse<T> { |
| #[inline] |
| fn partial_cmp(&self, other: &Reverse<T>) -> Option<Ordering> { |
| other.0.partial_cmp(&self.0) |
| } |
| |
| #[inline] |
| fn lt(&self, other: &Self) -> bool { other.0 < self.0 } |
| #[inline] |
| fn le(&self, other: &Self) -> bool { other.0 <= self.0 } |
| #[inline] |
| fn ge(&self, other: &Self) -> bool { other.0 >= self.0 } |
| #[inline] |
| fn gt(&self, other: &Self) -> bool { other.0 > self.0 } |
| } |
| |
| #[stable(feature = "reverse_cmp_key", since = "1.19.0")] |
| impl<T: Ord> Ord for Reverse<T> { |
| #[inline] |
| fn cmp(&self, other: &Reverse<T>) -> Ordering { |
| other.0.cmp(&self.0) |
| } |
| } |
| |
| /// Trait for types that form a [total order](https://en.wikipedia.org/wiki/Total_order). |
| /// |
| /// An order is a total order if it is (for all `a`, `b` and `c`): |
| /// |
| /// - total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is true; and |
| /// - transitive, `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`. |
| /// |
| /// ## Derivable |
| /// |
| /// This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a |
| /// lexicographic ordering based on the top-to-bottom declaration order of the struct's members. |
| /// When `derive`d on enums, variants are ordered by their top-to-bottom declaration order. |
| /// |
| /// ## How can I implement `Ord`? |
| /// |
| /// `Ord` requires that the type also be `PartialOrd` and `Eq` (which requires `PartialEq`). |
| /// |
| /// Then you must define an implementation for `cmp()`. You may find it useful to use |
| /// `cmp()` on your type's fields. |
| /// |
| /// Implementations of `PartialEq`, `PartialOrd`, and `Ord` *must* |
| /// agree with each other. That is, `a.cmp(b) == Ordering::Equal` if |
| /// and only if `a == b` and `Some(a.cmp(b)) == a.partial_cmp(b)` for |
| /// all `a` and `b`. It's easy to accidentally make them disagree by |
| /// deriving some of the traits and manually implementing others. |
| /// |
| /// Here's an example where you want to sort people by height only, disregarding `id` |
| /// and `name`: |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// #[derive(Eq)] |
| /// struct Person { |
| /// id: u32, |
| /// name: String, |
| /// height: u32, |
| /// } |
| /// |
| /// impl Ord for Person { |
| /// fn cmp(&self, other: &Person) -> Ordering { |
| /// self.height.cmp(&other.height) |
| /// } |
| /// } |
| /// |
| /// impl PartialOrd for Person { |
| /// fn partial_cmp(&self, other: &Person) -> Option<Ordering> { |
| /// Some(self.cmp(other)) |
| /// } |
| /// } |
| /// |
| /// impl PartialEq for Person { |
| /// fn eq(&self, other: &Person) -> bool { |
| /// self.height == other.height |
| /// } |
| /// } |
| /// ``` |
| #[lang = "ord"] |
| #[doc(alias = "<")] |
| #[doc(alias = ">")] |
| #[doc(alias = "<=")] |
| #[doc(alias = ">=")] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub trait Ord: Eq + PartialOrd<Self> { |
| /// This method returns an `Ordering` between `self` and `other`. |
| /// |
| /// By convention, `self.cmp(&other)` returns the ordering matching the expression |
| /// `self <operator> other` if true. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// assert_eq!(5.cmp(&10), Ordering::Less); |
| /// assert_eq!(10.cmp(&5), Ordering::Greater); |
| /// assert_eq!(5.cmp(&5), Ordering::Equal); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn cmp(&self, other: &Self) -> Ordering; |
| |
| /// Compares and returns the maximum of two values. |
| /// |
| /// Returns the second argument if the comparison determines them to be equal. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// assert_eq!(2, 1.max(2)); |
| /// assert_eq!(2, 2.max(2)); |
| /// ``` |
| #[stable(feature = "ord_max_min", since = "1.21.0")] |
| #[inline] |
| fn max(self, other: Self) -> Self |
| where Self: Sized { |
| if other >= self { other } else { self } |
| } |
| |
| /// Compares and returns the minimum of two values. |
| /// |
| /// Returns the first argument if the comparison determines them to be equal. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// assert_eq!(1, 1.min(2)); |
| /// assert_eq!(2, 2.min(2)); |
| /// ``` |
| #[stable(feature = "ord_max_min", since = "1.21.0")] |
| #[inline] |
| fn min(self, other: Self) -> Self |
| where Self: Sized { |
| if self <= other { self } else { other } |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Eq for Ordering {} |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Ord for Ordering { |
| #[inline] |
| fn cmp(&self, other: &Ordering) -> Ordering { |
| (*self as i32).cmp(&(*other as i32)) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialOrd for Ordering { |
| #[inline] |
| fn partial_cmp(&self, other: &Ordering) -> Option<Ordering> { |
| (*self as i32).partial_cmp(&(*other as i32)) |
| } |
| } |
| |
| /// Trait for values that can be compared for a sort-order. |
| /// |
| /// The comparison must satisfy, for all `a`, `b` and `c`: |
| /// |
| /// - antisymmetry: if `a < b` then `!(a > b)`, as well as `a > b` implying `!(a < b)`; and |
| /// - transitivity: `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`. |
| /// |
| /// Note that these requirements mean that the trait itself must be implemented symmetrically and |
| /// transitively: if `T: PartialOrd<U>` and `U: PartialOrd<V>` then `U: PartialOrd<T>` and `T: |
| /// PartialOrd<V>`. |
| /// |
| /// ## Derivable |
| /// |
| /// This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a |
| /// lexicographic ordering based on the top-to-bottom declaration order of the struct's members. |
| /// When `derive`d on enums, variants are ordered by their top-to-bottom declaration order. |
| /// |
| /// ## How can I implement `PartialOrd`? |
| /// |
| /// `PartialOrd` only requires implementation of the `partial_cmp` method, with the others |
| /// generated from default implementations. |
| /// |
| /// However it remains possible to implement the others separately for types which do not have a |
| /// total order. For example, for floating point numbers, `NaN < 0 == false` and `NaN >= 0 == |
| /// false` (cf. IEEE 754-2008 section 5.11). |
| /// |
| /// `PartialOrd` requires your type to be `PartialEq`. |
| /// |
| /// Implementations of `PartialEq`, `PartialOrd`, and `Ord` *must* agree with each other. It's |
| /// easy to accidentally make them disagree by deriving some of the traits and manually |
| /// implementing others. |
| /// |
| /// If your type is `Ord`, you can implement `partial_cmp()` by using `cmp()`: |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// #[derive(Eq)] |
| /// struct Person { |
| /// id: u32, |
| /// name: String, |
| /// height: u32, |
| /// } |
| /// |
| /// impl PartialOrd for Person { |
| /// fn partial_cmp(&self, other: &Person) -> Option<Ordering> { |
| /// Some(self.cmp(other)) |
| /// } |
| /// } |
| /// |
| /// impl Ord for Person { |
| /// fn cmp(&self, other: &Person) -> Ordering { |
| /// self.height.cmp(&other.height) |
| /// } |
| /// } |
| /// |
| /// impl PartialEq for Person { |
| /// fn eq(&self, other: &Person) -> bool { |
| /// self.height == other.height |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// You may also find it useful to use `partial_cmp()` on your type's fields. Here |
| /// is an example of `Person` types who have a floating-point `height` field that |
| /// is the only field to be used for sorting: |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// struct Person { |
| /// id: u32, |
| /// name: String, |
| /// height: f64, |
| /// } |
| /// |
| /// impl PartialOrd for Person { |
| /// fn partial_cmp(&self, other: &Person) -> Option<Ordering> { |
| /// self.height.partial_cmp(&other.height) |
| /// } |
| /// } |
| /// |
| /// impl PartialEq for Person { |
| /// fn eq(&self, other: &Person) -> bool { |
| /// self.height == other.height |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x : u32 = 0; |
| /// let y : u32 = 1; |
| /// |
| /// assert_eq!(x < y, true); |
| /// assert_eq!(x.lt(&y), true); |
| /// ``` |
| #[lang = "partial_ord"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[doc(alias = ">")] |
| #[doc(alias = "<")] |
| #[doc(alias = "<=")] |
| #[doc(alias = ">=")] |
| #[rustc_on_unimplemented( |
| message="can't compare `{Self}` with `{Rhs}`", |
| label="no implementation for `{Self} < {Rhs}` and `{Self} > {Rhs}`", |
| )] |
| pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> { |
| /// This method returns an ordering between `self` and `other` values if one exists. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp::Ordering; |
| /// |
| /// let result = 1.0.partial_cmp(&2.0); |
| /// assert_eq!(result, Some(Ordering::Less)); |
| /// |
| /// let result = 1.0.partial_cmp(&1.0); |
| /// assert_eq!(result, Some(Ordering::Equal)); |
| /// |
| /// let result = 2.0.partial_cmp(&1.0); |
| /// assert_eq!(result, Some(Ordering::Greater)); |
| /// ``` |
| /// |
| /// When comparison is impossible: |
| /// |
| /// ``` |
| /// let result = std::f64::NAN.partial_cmp(&1.0); |
| /// assert_eq!(result, None); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn partial_cmp(&self, other: &Rhs) -> Option<Ordering>; |
| |
| /// This method tests less than (for `self` and `other`) and is used by the `<` operator. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let result = 1.0 < 2.0; |
| /// assert_eq!(result, true); |
| /// |
| /// let result = 2.0 < 1.0; |
| /// assert_eq!(result, false); |
| /// ``` |
| #[inline] |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn lt(&self, other: &Rhs) -> bool { |
| match self.partial_cmp(other) { |
| Some(Less) => true, |
| _ => false, |
| } |
| } |
| |
| /// This method tests less than or equal to (for `self` and `other`) and is used by the `<=` |
| /// operator. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let result = 1.0 <= 2.0; |
| /// assert_eq!(result, true); |
| /// |
| /// let result = 2.0 <= 2.0; |
| /// assert_eq!(result, true); |
| /// ``` |
| #[inline] |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn le(&self, other: &Rhs) -> bool { |
| match self.partial_cmp(other) { |
| Some(Less) | Some(Equal) => true, |
| _ => false, |
| } |
| } |
| |
| /// This method tests greater than (for `self` and `other`) and is used by the `>` operator. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let result = 1.0 > 2.0; |
| /// assert_eq!(result, false); |
| /// |
| /// let result = 2.0 > 2.0; |
| /// assert_eq!(result, false); |
| /// ``` |
| #[inline] |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn gt(&self, other: &Rhs) -> bool { |
| match self.partial_cmp(other) { |
| Some(Greater) => true, |
| _ => false, |
| } |
| } |
| |
| /// This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` |
| /// operator. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let result = 2.0 >= 1.0; |
| /// assert_eq!(result, true); |
| /// |
| /// let result = 2.0 >= 2.0; |
| /// assert_eq!(result, true); |
| /// ``` |
| #[inline] |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| fn ge(&self, other: &Rhs) -> bool { |
| match self.partial_cmp(other) { |
| Some(Greater) | Some(Equal) => true, |
| _ => false, |
| } |
| } |
| } |
| |
| /// Compares and returns the minimum of two values. |
| /// |
| /// Returns the first argument if the comparison determines them to be equal. |
| /// |
| /// Internally uses an alias to `Ord::min`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp; |
| /// |
| /// assert_eq!(1, cmp::min(1, 2)); |
| /// assert_eq!(2, cmp::min(2, 2)); |
| /// ``` |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn min<T: Ord>(v1: T, v2: T) -> T { |
| v1.min(v2) |
| } |
| |
| /// Compares and returns the maximum of two values. |
| /// |
| /// Returns the second argument if the comparison determines them to be equal. |
| /// |
| /// Internally uses an alias to `Ord::max`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::cmp; |
| /// |
| /// assert_eq!(2, cmp::max(1, 2)); |
| /// assert_eq!(2, cmp::max(2, 2)); |
| /// ``` |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn max<T: Ord>(v1: T, v2: T) -> T { |
| v1.max(v2) |
| } |
| |
| // Implementation of PartialEq, Eq, PartialOrd and Ord for primitive types |
| mod impls { |
| use cmp::Ordering::{self, Less, Greater, Equal}; |
| |
| macro_rules! partial_eq_impl { |
| ($($t:ty)*) => ($( |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialEq for $t { |
| #[inline] |
| fn eq(&self, other: &$t) -> bool { (*self) == (*other) } |
| #[inline] |
| fn ne(&self, other: &$t) -> bool { (*self) != (*other) } |
| } |
| )*) |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialEq for () { |
| #[inline] |
| fn eq(&self, _other: &()) -> bool { true } |
| #[inline] |
| fn ne(&self, _other: &()) -> bool { false } |
| } |
| |
| partial_eq_impl! { |
| bool char usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 |
| } |
| |
| macro_rules! eq_impl { |
| ($($t:ty)*) => ($( |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Eq for $t {} |
| )*) |
| } |
| |
| eq_impl! { () bool char usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 } |
| |
| macro_rules! partial_ord_impl { |
| ($($t:ty)*) => ($( |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialOrd for $t { |
| #[inline] |
| fn partial_cmp(&self, other: &$t) -> Option<Ordering> { |
| match (self <= other, self >= other) { |
| (false, false) => None, |
| (false, true) => Some(Greater), |
| (true, false) => Some(Less), |
| (true, true) => Some(Equal), |
| } |
| } |
| #[inline] |
| fn lt(&self, other: &$t) -> bool { (*self) < (*other) } |
| #[inline] |
| fn le(&self, other: &$t) -> bool { (*self) <= (*other) } |
| #[inline] |
| fn ge(&self, other: &$t) -> bool { (*self) >= (*other) } |
| #[inline] |
| fn gt(&self, other: &$t) -> bool { (*self) > (*other) } |
| } |
| )*) |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialOrd for () { |
| #[inline] |
| fn partial_cmp(&self, _: &()) -> Option<Ordering> { |
| Some(Equal) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialOrd for bool { |
| #[inline] |
| fn partial_cmp(&self, other: &bool) -> Option<Ordering> { |
| (*self as u8).partial_cmp(&(*other as u8)) |
| } |
| } |
| |
| partial_ord_impl! { f32 f64 } |
| |
| macro_rules! ord_impl { |
| ($($t:ty)*) => ($( |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl PartialOrd for $t { |
| #[inline] |
| fn partial_cmp(&self, other: &$t) -> Option<Ordering> { |
| Some(self.cmp(other)) |
| } |
| #[inline] |
| fn lt(&self, other: &$t) -> bool { (*self) < (*other) } |
| #[inline] |
| fn le(&self, other: &$t) -> bool { (*self) <= (*other) } |
| #[inline] |
| fn ge(&self, other: &$t) -> bool { (*self) >= (*other) } |
| #[inline] |
| fn gt(&self, other: &$t) -> bool { (*self) > (*other) } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Ord for $t { |
| #[inline] |
| fn cmp(&self, other: &$t) -> Ordering { |
| if *self == *other { Equal } |
| else if *self < *other { Less } |
| else { Greater } |
| } |
| } |
| )*) |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Ord for () { |
| #[inline] |
| fn cmp(&self, _other: &()) -> Ordering { Equal } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl Ord for bool { |
| #[inline] |
| fn cmp(&self, other: &bool) -> Ordering { |
| (*self as u8).cmp(&(*other as u8)) |
| } |
| } |
| |
| ord_impl! { char usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 } |
| |
| #[unstable(feature = "never_type", issue = "35121")] |
| impl PartialEq for ! { |
| fn eq(&self, _: &!) -> bool { |
| *self |
| } |
| } |
| |
| #[unstable(feature = "never_type", issue = "35121")] |
| impl Eq for ! {} |
| |
| #[unstable(feature = "never_type", issue = "35121")] |
| impl PartialOrd for ! { |
| fn partial_cmp(&self, _: &!) -> Option<Ordering> { |
| *self |
| } |
| } |
| |
| #[unstable(feature = "never_type", issue = "35121")] |
| impl Ord for ! { |
| fn cmp(&self, _: &!) -> Ordering { |
| *self |
| } |
| } |
| |
| // & pointers |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a A where A: PartialEq<B> { |
| #[inline] |
| fn eq(&self, other: & &'b B) -> bool { PartialEq::eq(*self, *other) } |
| #[inline] |
| fn ne(&self, other: & &'b B) -> bool { PartialEq::ne(*self, *other) } |
| } |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b B> for &'a A where A: PartialOrd<B> { |
| #[inline] |
| fn partial_cmp(&self, other: &&'b B) -> Option<Ordering> { |
| PartialOrd::partial_cmp(*self, *other) |
| } |
| #[inline] |
| fn lt(&self, other: & &'b B) -> bool { PartialOrd::lt(*self, *other) } |
| #[inline] |
| fn le(&self, other: & &'b B) -> bool { PartialOrd::le(*self, *other) } |
| #[inline] |
| fn ge(&self, other: & &'b B) -> bool { PartialOrd::ge(*self, *other) } |
| #[inline] |
| fn gt(&self, other: & &'b B) -> bool { PartialOrd::gt(*self, *other) } |
| } |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<A: ?Sized> Ord for &A where A: Ord { |
| #[inline] |
| fn cmp(&self, other: &Self) -> Ordering { Ord::cmp(*self, *other) } |
| } |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<A: ?Sized> Eq for &A where A: Eq {} |
| |
| // &mut pointers |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a mut A where A: PartialEq<B> { |
| #[inline] |
| fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) } |
| #[inline] |
| fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) } |
| } |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, 'b, A: ?Sized, B: ?Sized> PartialOrd<&'b mut B> for &'a mut A where A: PartialOrd<B> { |
| #[inline] |
| fn partial_cmp(&self, other: &&'b mut B) -> Option<Ordering> { |
| PartialOrd::partial_cmp(*self, *other) |
| } |
| #[inline] |
| fn lt(&self, other: &&'b mut B) -> bool { PartialOrd::lt(*self, *other) } |
| #[inline] |
| fn le(&self, other: &&'b mut B) -> bool { PartialOrd::le(*self, *other) } |
| #[inline] |
| fn ge(&self, other: &&'b mut B) -> bool { PartialOrd::ge(*self, *other) } |
| #[inline] |
| fn gt(&self, other: &&'b mut B) -> bool { PartialOrd::gt(*self, *other) } |
| } |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<A: ?Sized> Ord for &mut A where A: Ord { |
| #[inline] |
| fn cmp(&self, other: &Self) -> Ordering { Ord::cmp(*self, *other) } |
| } |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<A: ?Sized> Eq for &mut A where A: Eq {} |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b mut B> for &'a A where A: PartialEq<B> { |
| #[inline] |
| fn eq(&self, other: &&'b mut B) -> bool { PartialEq::eq(*self, *other) } |
| #[inline] |
| fn ne(&self, other: &&'b mut B) -> bool { PartialEq::ne(*self, *other) } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, 'b, A: ?Sized, B: ?Sized> PartialEq<&'b B> for &'a mut A where A: PartialEq<B> { |
| #[inline] |
| fn eq(&self, other: &&'b B) -> bool { PartialEq::eq(*self, *other) } |
| #[inline] |
| fn ne(&self, other: &&'b B) -> bool { PartialEq::ne(*self, *other) } |
| } |
| } |