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`//! 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`] is an enum returned by the main functions of [`Ord`] and //! [`PartialOrd`], and describes an ordering. //! * [`Reverse`] is a struct that allows you to easily reverse an ordering. //! * [`max`] and [`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. //! //! [`Eq`]: trait.Eq.html //! [`PartialEq`]: trait.PartialEq.html //! [`Ord`]: trait.Ord.html //! [`PartialOrd`]: trait.PartialOrd.html //! [`Ordering`]: enum.Ordering.html //! [`Reverse`]: struct.Reverse.html //! [`max`]: fn.max.html //! [`min`]: fn.min.html #![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: &Self) -> 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: /// /// ``` /// // The derive implements <BookFormat> == <BookFormat> comparisons /// #[derive(PartialEq)] /// enum BookFormat { /// Paperback, /// Hardback, /// Ebook, /// } /// /// struct Book { /// isbn: i32, /// format: BookFormat, /// } /// /// // Implement <Book> == <BookFormat> comparisons /// impl PartialEq<BookFormat> for Book { /// fn eq(&self, other: &BookFormat) -> bool { /// self.format == *other /// } /// } /// /// // Implement <BookFormat> == <Book> comparisons /// impl PartialEq<Book> for BookFormat { /// fn eq(&self, other: &Book) -> bool { /// *self == other.format /// } /// } /// /// let b1 = Book { isbn: 3, format: BookFormat::Paperback }; /// /// assert!(b1 == BookFormat::Paperback); /// assert!(BookFormat::Ebook != b1); /// ``` /// /// By changing `impl PartialEq for Book` to `impl PartialEq<BookFormat> for Book`, /// we allow `BookFormat`s to be compared with `Book`s. /// /// A comparison like the one above, which ignores some fields of the struct, /// can be dangerous. It can easily lead to an unintended violation of the /// requirements for a partial equivalence relation. For example, if we kept /// the above implementation of `PartialEq<Book>` for `BookFormat` and added an /// implementation of `PartialEq<Book>` for `Book` (either via a `#[derive]` or /// via the manual implementation from the first example) then the result would /// violate transitivity: /// /// ```should_panic /// #[derive(PartialEq)] /// enum BookFormat { /// Paperback, /// Hardback, /// Ebook, /// } /// /// #[derive(PartialEq)] /// struct Book { /// isbn: i32, /// format: BookFormat, /// } /// /// impl PartialEq<BookFormat> for Book { /// fn eq(&self, other: &BookFormat) -> bool { /// self.format == *other /// } /// } /// /// impl PartialEq<Book> for BookFormat { /// fn eq(&self, other: &Book) -> bool { /// *self == other.format /// } /// } /// /// fn main() { /// let b1 = Book { isbn: 1, format: BookFormat::Paperback }; /// let b2 = Book { isbn: 2, format: BookFormat::Paperback }; /// /// assert!(b1 == BookFormat::Paperback); /// assert!(BookFormat::Paperback == b2); /// /// // The following should hold by transitivity but doesn't. /// assert!(b1 == b2); // <-- PANICS /// } /// ``` /// /// # 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) } } /// Derive macro generating an impl of the trait `PartialEq`. #[rustc_builtin_macro] #[stable(feature = "builtin_macro_prelude", since = "1.38.0")] #[allow_internal_unstable(core_intrinsics, structural_match)] pub macro PartialEq($item:item) { /* compiler built-in */ } /// 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: &Self) -> 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) {} } /// Derive macro generating an impl of the trait `Eq`. #[rustc_builtin_macro] #[stable(feature = "builtin_macro_prelude", since = "1.38.0")] #[allow_internal_unstable(core_intrinsics, derive_eq, structural_match)] pub macro Eq($item:item) { /* compiler built-in */ } // 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: crate::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 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 gt(&self, other: &Self) -> bool { other.0 > self.0 } #[inline] fn ge(&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: &Self) -> Ordering { /// self.height.cmp(&other.height) /// } /// } /// /// impl PartialOrd for Person { /// fn partial_cmp(&self, other: &Self) -> Option<Ordering> { /// Some(self.cmp(other)) /// } /// } /// /// impl PartialEq for Person { /// fn eq(&self, other: &Self) -> bool { /// self.height == other.height /// } /// } /// ``` #[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 { max_by(self, other, Ord::cmp) } /// 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 { min_by(self, other, Ord::cmp) } /// Restrict a value to a certain interval. /// /// Returns `max` if `self` is greater than `max`, and `min` if `self` is /// less than `min`. Otherwise this returns `self`. /// /// # Panics /// /// Panics if `min > max`. /// /// # Examples /// /// ``` /// #![feature(clamp)] /// /// assert!((-3).clamp(-2, 1) == -2); /// assert!(0.clamp(-2, 1) == 0); /// assert!(2.clamp(-2, 1) == 1); /// ``` #[unstable(feature = "clamp", issue = "44095")] fn clamp(self, min: Self, max: Self) -> Self where Self: Sized { assert!(min <= max); if self < min { min } else if self > max { max } else { self } } } /// Derive macro generating an impl of the trait `Ord`. #[rustc_builtin_macro] #[stable(feature = "builtin_macro_prelude", since = "1.38.0")] #[allow_internal_unstable(core_intrinsics)] pub macro Ord($item:item) { /* compiler built-in */ } #[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: &Self) -> Option<Ordering> { /// self.height.partial_cmp(&other.height) /// } /// } /// /// impl PartialEq for Person { /// fn eq(&self, other: &Self) -> 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, } } } /// Derive macro generating an impl of the trait `PartialOrd`. #[rustc_builtin_macro] #[stable(feature = "builtin_macro_prelude", since = "1.38.0")] #[allow_internal_unstable(core_intrinsics)] pub macro PartialOrd($item:item) { /* compiler built-in */ } /// 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) } /// Returns the minimum of two values with respect to the specified comparison function. /// /// Returns the first argument if the comparison determines them to be equal. /// /// # Examples /// /// ``` /// #![feature(cmp_min_max_by)] /// /// use std::cmp; /// /// assert_eq!(cmp::min_by(-2, 1, |x: &i32, y: &i32| x.abs().cmp(&y.abs())), 1); /// assert_eq!(cmp::min_by(-2, 2, |x: &i32, y: &i32| x.abs().cmp(&y.abs())), -2); /// ``` #[inline] #[unstable(feature = "cmp_min_max_by", issue = "64460")] pub fn min_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T { match compare(&v1, &v2) { Ordering::Less | Ordering::Equal => v1, Ordering::Greater => v2, } } /// Returns the element that gives the minimum value from the specified function. /// /// Returns the first argument if the comparison determines them to be equal. /// /// # Examples /// /// ``` /// #![feature(cmp_min_max_by)] /// /// use std::cmp; /// /// assert_eq!(cmp::min_by_key(-2, 1, |x: &i32| x.abs()), 1); /// assert_eq!(cmp::min_by_key(-2, 2, |x: &i32| x.abs()), -2); /// ``` #[inline] #[unstable(feature = "cmp_min_max_by", issue = "64460")] pub fn min_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T { min_by(v1, v2, |v1, v2| f(v1).cmp(&f(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) } /// Returns the maximum of two values with respect to the specified comparison function. /// /// Returns the second argument if the comparison determines them to be equal. /// /// # Examples /// /// ``` /// #![feature(cmp_min_max_by)] /// /// use std::cmp; /// /// assert_eq!(cmp::max_by(-2, 1, |x: &i32, y: &i32| x.abs().cmp(&y.abs())), -2); /// assert_eq!(cmp::max_by(-2, 2, |x: &i32, y: &i32| x.abs().cmp(&y.abs())), 2); /// ``` #[inline] #[unstable(feature = "cmp_min_max_by", issue = "64460")] pub fn max_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T { match compare(&v1, &v2) { Ordering::Less | Ordering::Equal => v2, Ordering::Greater => v1, } } /// Returns the element that gives the maximum value from the specified function. /// /// Returns the second argument if the comparison determines them to be equal. /// /// # Examples /// /// ``` /// #![feature(cmp_min_max_by)] /// /// use std::cmp; /// /// assert_eq!(cmp::max_by_key(-2, 1, |x: &i32| x.abs()), -2); /// assert_eq!(cmp::max_by_key(-2, 2, |x: &i32| x.abs()), 2); /// ``` #[inline] #[unstable(feature = "cmp_min_max_by", issue = "64460")] pub fn max_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T { max_by(v1, v2, |v1, v2| f(v1).cmp(&f(v2))) } // Implementation of PartialEq, Eq, PartialOrd and Ord for primitive types mod impls { use crate::hint::unreachable_unchecked; use crate::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 { // The order here is important to generate more optimal assembly. // See <https://github.com/rust-lang/rust/issues/63758> for more info. if *self < *other { Less } else if *self == *other { Equal } 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 { // Casting to i8's and converting the difference to an Ordering generates // more optimal assembly. // See <https://github.com/rust-lang/rust/issues/66780> for more info. match (*self as i8) - (*other as i8) { -1 => Less, 0 => Equal, 1 => Greater, // SAFETY: bool as i8 returns 0 or 1, so the difference can't be anything else _ => unsafe { unreachable_unchecked() }, } } } 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: ?Sized, B: ?Sized> PartialEq<&B> for &A where A: PartialEq<B> { #[inline] fn eq(&self, other: & &B) -> bool { PartialEq::eq(*self, *other) } #[inline] fn ne(&self, other: & &B) -> bool { PartialEq::ne(*self, *other) } } #[stable(feature = "rust1", since = "1.0.0")] impl<A: ?Sized, B: ?Sized> PartialOrd<&B> for &A where A: PartialOrd<B> { #[inline] fn partial_cmp(&self, other: &&B) -> Option<Ordering> { PartialOrd::partial_cmp(*self, *other) } #[inline] fn lt(&self, other: & &B) -> bool { PartialOrd::lt(*self, *other) } #[inline] fn le(&self, other: & &B) -> bool { PartialOrd::le(*self, *other) } #[inline] fn gt(&self, other: & &B) -> bool { PartialOrd::gt(*self, *other) } #[inline] fn ge(&self, other: & &B) -> bool { PartialOrd::ge(*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: ?Sized, B: ?Sized> PartialEq<&mut B> for &mut A where A: PartialEq<B> { #[inline] fn eq(&self, other: &&mut B) -> bool { PartialEq::eq(*self, *other) } #[inline] fn ne(&self, other: &&mut B) -> bool { PartialEq::ne(*self, *other) } } #[stable(feature = "rust1", since = "1.0.0")] impl<A: ?Sized, B: ?Sized> PartialOrd<&mut B> for &mut A where A: PartialOrd<B> { #[inline] fn partial_cmp(&self, other: &&mut B) -> Option<Ordering> { PartialOrd::partial_cmp(*self, *other) } #[inline] fn lt(&self, other: &&mut B) -> bool { PartialOrd::lt(*self, *other) } #[inline] fn le(&self, other: &&mut B) -> bool { PartialOrd::le(*self, *other) } #[inline] fn gt(&self, other: &&mut B) -> bool { PartialOrd::gt(*self, *other) } #[inline] fn ge(&self, other: &&mut B) -> bool { PartialOrd::ge(*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: ?Sized, B: ?Sized> PartialEq<&mut B> for &A where A: PartialEq<B> { #[inline] fn eq(&self, other: &&mut B) -> bool { PartialEq::eq(*self, *other) } #[inline] fn ne(&self, other: &&mut B) -> bool { PartialEq::ne(*self, *other) } } #[stable(feature = "rust1", since = "1.0.0")] impl<A: ?Sized, B: ?Sized> PartialEq<&B> for &mut A where A: PartialEq<B> { #[inline] fn eq(&self, other: &&B) -> bool { PartialEq::eq(*self, *other) } #[inline] fn ne(&self, other: &&B) -> bool { PartialEq::ne(*self, *other) } } }`