1.0.0[][src]Trait std::cmp::Ord

#[lang = "ord"]
pub trait Ord: Eq + PartialOrd<Self> { fn cmp(&self, other: &Self) -> Ordering; fn max(self, other: Self) -> Self { ... }
fn min(self, other: Self) -> Self { ... } }

Trait for types that form a total order.

An order is a total order if it is (for all a, b and c):

Derivable

This trait can be used with #[derive]. When derived on structs, it will produce a lexicographic ordering based on the top-to-bottom declaration order of the struct's members. When derived 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. 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
    }
}Run

Required Methods

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);Run

Provided Methods

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));Run

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));Run

Implementations on Foreign Types

impl Ord for CpuidResult
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Implementors

impl Ord for Ordering
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impl Ord for ErrorKind
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impl Ord for IpAddr
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impl Ord for bool
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impl Ord for char
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impl Ord for i128
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impl Ord for i16
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impl Ord for i32
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impl Ord for i64
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impl Ord for i8
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impl Ord for isize
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impl Ord for !
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impl Ord for str
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Implements ordering of strings.

Strings are ordered lexicographically by their byte values. This orders Unicode code points based on their positions in the code charts. This is not necessarily the same as "alphabetical" order, which varies by language and locale. Sorting strings according to culturally-accepted standards requires locale-specific data that is outside the scope of the str type.

impl Ord for u128
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impl Ord for u16
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impl Ord for u32
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impl Ord for u64
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impl Ord for u8
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impl Ord for ()
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impl Ord for usize
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impl Ord for TypeId
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impl Ord for UnicodeVersion
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impl Ord for CStr
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impl Ord for CString
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impl Ord for OsStr
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impl Ord for OsString
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impl Ord for Error
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impl Ord for PhantomPinned
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impl Ord for Ipv4Addr
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impl Ord for Ipv6Addr
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impl Ord for NonZeroU128
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impl Ord for NonZeroU16
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impl Ord for NonZeroU32
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impl Ord for NonZeroU64
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impl Ord for NonZeroU8
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impl Ord for NonZeroUsize
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impl Ord for NoneError
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impl Ord for Path
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impl Ord for PathBuf
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impl Ord for String
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impl Ord for Duration
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impl Ord for Instant
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impl Ord for SystemTime
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impl<'_, A> Ord for &'_ A where
    A: Ord + ?Sized
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impl<'_, A> Ord for &'_ mut A where
    A: Ord + ?Sized
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impl<'a> Ord for Component<'a>
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impl<'a> Ord for Prefix<'a>
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impl<'a> Ord for Components<'a>
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impl<'a> Ord for PrefixComponent<'a>
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impl<'a, B> Ord for Cow<'a, B> where
    B: Ord + ToOwned + ?Sized
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impl<A> Ord for (A,) where
    A: Ord + ?Sized
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impl<A> Ord for VecDeque<A> where
    A: Ord
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impl<A, B> Ord for (A, B) where
    A: Ord,
    B: Ord + ?Sized
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impl<A, B, C> Ord for (A, B, C) where
    A: Ord,
    B: Ord,
    C: Ord + ?Sized
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impl<A, B, C, D> Ord for (A, B, C, D) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord + ?Sized
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impl<A, B, C, D, E> Ord for (A, B, C, D, E) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord + ?Sized
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impl<A, B, C, D, E, F> Ord for (A, B, C, D, E, F) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord + ?Sized
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impl<A, B, C, D, E, F, G> Ord for (A, B, C, D, E, F, G) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord,
    G: Ord + ?Sized
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impl<A, B, C, D, E, F, G, H> Ord for (A, B, C, D, E, F, G, H) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord,
    G: Ord,
    H: Ord + ?Sized
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impl<A, B, C, D, E, F, G, H, I> Ord for (A, B, C, D, E, F, G, H, I) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord,
    G: Ord,
    H: Ord,
    I: Ord + ?Sized
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impl<A, B, C, D, E, F, G, H, I, J> Ord for (A, B, C, D, E, F, G, H, I, J) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord,
    G: Ord,
    H: Ord,
    I: Ord,
    J: Ord + ?Sized
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impl<A, B, C, D, E, F, G, H, I, J, K> Ord for (A, B, C, D, E, F, G, H, I, J, K) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord,
    G: Ord,
    H: Ord,
    I: Ord,
    J: Ord,
    K: Ord + ?Sized
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impl<A, B, C, D, E, F, G, H, I, J, K, L> Ord for (A, B, C, D, E, F, G, H, I, J, K, L) where
    A: Ord,
    B: Ord,
    C: Ord,
    D: Ord,
    E: Ord,
    F: Ord,
    G: Ord,
    H: Ord,
    I: Ord,
    J: Ord,
    K: Ord,
    L: Ord + ?Sized
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impl<K, V> Ord for BTreeMap<K, V> where
    K: Ord,
    V: Ord
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impl<P> Ord for Pin<P> where
    P: Ord
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impl<Ret> Ord for fn() -> Ret
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impl<Ret> Ord for extern "C" fn() -> Ret
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impl<Ret> Ord for unsafe fn() -> Ret
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impl<Ret> Ord for unsafe extern "C" fn() -> Ret
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impl<Ret, A> Ord for fn(A) -> Ret
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impl<Ret, A> Ord for extern "C" fn(A) -> Ret
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impl<Ret, A> Ord for extern "C" fn(A, ...) -> Ret
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impl<Ret, A> Ord for unsafe fn(A) -> Ret
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impl<Ret, A> Ord for unsafe extern "C" fn(A) -> Ret
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impl<Ret, A> Ord for unsafe extern "C" fn(A, ...) -> Ret
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impl<Ret, A, B> Ord for fn(A, B) -> Ret
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impl<Ret, A, B> Ord for extern "C" fn(A, B) -> Ret
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impl<Ret, A, B> Ord for extern "C" fn(A, B, ...) -> Ret
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impl<Ret, A, B> Ord for unsafe fn(A, B) -> Ret
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impl<Ret, A, B> Ord for unsafe extern "C" fn(A, B) -> Ret
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impl<Ret, A, B> Ord for unsafe extern "C" fn(A, B, ...) -> Ret
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impl<Ret, A, B, C> Ord for fn(A, B, C) -> Ret
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impl<Ret, A, B, C> Ord for extern "C" fn(A, B, C) -> Ret
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impl<Ret, A, B, C> Ord for extern "C" fn(A, B, C, ...) -> Ret
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impl<Ret, A, B, C> Ord for unsafe fn(A, B, C) -> Ret
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impl<Ret, A, B, C> Ord for unsafe extern "C" fn(A, B, C) -> Ret
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impl<Ret, A, B, C> Ord for unsafe extern "C" fn(A, B, C, ...) -> Ret
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impl<Ret, A, B, C, D> Ord for fn(A, B, C, D) -> Ret
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impl<Ret, A, B, C, D> Ord for extern "C" fn(A, B, C, D) -> Ret
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impl<Ret, A, B, C, D> Ord for extern "C" fn(A, B, C, D, ...) -> Ret
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impl<Ret, A, B, C, D> Ord for unsafe fn(A, B, C, D) -> Ret
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impl<Ret, A, B, C, D> Ord for unsafe extern "C" fn(A, B, C, D) -> Ret
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impl<Ret, A, B, C, D> Ord for unsafe extern "C" fn(A, B, C, D, ...) -> Ret
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impl<Ret, A, B, C, D, E> Ord for fn(A, B, C, D, E) -> Ret
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impl<Ret, A, B, C, D, E> Ord for extern "C" fn(A, B, C, D, E) -> Ret
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impl<Ret, A, B, C, D, E> Ord for extern "C" fn(A, B, C, D, E, ...) -> Ret
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impl<Ret, A, B, C, D, E> Ord for unsafe fn(A, B, C, D, E) -> Ret
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impl<Ret, A, B, C, D, E> Ord for unsafe extern "C" fn(A, B, C, D, E) -> Ret
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impl<Ret, A, B, C, D, E> Ord for unsafe extern "C" fn(A, B, C, D, E, ...) -> Ret
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impl<Ret, A, B, C, D, E, F> Ord for fn(A, B, C, D, E, F) -> Ret
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impl<Ret, A, B, C, D, E, F> Ord for extern "C" fn(A, B, C, D, E, F) -> Ret
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impl<Ret, A, B, C, D, E, F> Ord for extern "C" fn(A, B, C, D, E, F, ...) -> Ret
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impl<Ret, A, B, C, D, E, F> Ord for unsafe fn(A, B, C, D, E, F) -> Ret
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impl<Ret, A, B, C, D, E, F> Ord for unsafe extern "C" fn(A, B, C, D, E, F) -> Ret
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impl<Ret, A, B, C, D, E, F> Ord for unsafe extern "C" fn(A, B, C, D, E, F, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G> Ord for fn(A, B, C, D, E, F, G) -> Ret
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impl<Ret, A, B, C, D, E, F, G> Ord for extern "C" fn(A, B, C, D, E, F, G) -> Ret
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impl<Ret, A, B, C, D, E, F, G> Ord for extern "C" fn(A, B, C, D, E, F, G, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G> Ord for unsafe fn(A, B, C, D, E, F, G) -> Ret
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impl<Ret, A, B, C, D, E, F, G> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G) -> Ret
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impl<Ret, A, B, C, D, E, F, G> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H> Ord for fn(A, B, C, D, E, F, G, H) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H> Ord for extern "C" fn(A, B, C, D, E, F, G, H) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H> Ord for extern "C" fn(A, B, C, D, E, F, G, H, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H> Ord for unsafe fn(A, B, C, D, E, F, G, H) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I> Ord for fn(A, B, C, D, E, F, G, H, I) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I> Ord for unsafe fn(A, B, C, D, E, F, G, H, I) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for fn(A, B, C, D, E, F, G, H, I, J) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, J, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for unsafe fn(A, B, C, D, E, F, G, H, I, J) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for unsafe fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L, ...) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for unsafe fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
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impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L, ...) -> Ret
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impl<T> Ord for Option<T> where
    T: Ord
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impl<T> Ord for Poll<T> where
    T: Ord
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impl<T> Ord for [T; 0] where
    T: Ord
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impl<T> Ord for [T; 1] where
    T: Ord
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impl<T> Ord for [T; 2] where
    T: Ord
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impl<T> Ord for [T; 3] where
    T: Ord
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impl<T> Ord for [T; 4] where
    T: Ord
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impl<T> Ord for [T; 5] where
    T: Ord
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impl<T> Ord for [T; 6] where
    T: Ord
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impl<T> Ord for [T; 7] where
    T: Ord
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impl<T> Ord for [T; 8] where
    T: Ord
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impl<T> Ord for [T; 9] where
    T: Ord
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impl<T> Ord for [T; 10] where
    T: Ord
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impl<T> Ord for [T; 11] where
    T: Ord
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impl<T> Ord for [T; 12] where
    T: Ord
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impl<T> Ord for [T; 13] where
    T: Ord
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impl<T> Ord for [T; 14] where
    T: Ord
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impl<T> Ord for [T; 15] where
    T: Ord
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impl<T> Ord for [T; 16] where
    T: Ord
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impl<T> Ord for [T; 17] where
    T: Ord
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impl<T> Ord for [T; 18] where
    T: Ord
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impl<T> Ord for [T; 19] where
    T: Ord
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impl<T> Ord for [T; 20] where
    T: Ord
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impl<T> Ord for [T; 21] where
    T: Ord
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impl<T> Ord for [T; 22] where
    T: Ord
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impl<T> Ord for [T; 23] where
    T: Ord
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impl<T> Ord for [T; 24] where
    T: Ord
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impl<T> Ord for [T; 25] where
    T: Ord
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impl<T> Ord for [T; 26] where
    T: Ord
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impl<T> Ord for [T; 27] where
    T: Ord
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impl<T> Ord for [T; 28] where
    T: Ord
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impl<T> Ord for [T; 29] where
    T: Ord
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impl<T> Ord for [T; 30] where
    T: Ord
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impl<T> Ord for [T; 31] where
    T: Ord
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impl<T> Ord for [T; 32] where
    T: Ord
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impl<T> Ord for *const T where
    T: ?Sized
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impl<T> Ord for *mut T where
    T: ?Sized
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impl<T> Ord for [T] where
    T: Ord
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Implements comparison of vectors lexicographically.

impl<T> Ord for Box<T> where
    T: Ord + ?Sized
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impl<T> Ord for Cell<T> where
    T: Copy + Ord
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impl<T> Ord for RefCell<T> where
    T: Ord + ?Sized
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Panics

Panics if the value in either RefCell is currently borrowed.

impl<T> Ord for Reverse<T> where
    T: Ord
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impl<T> Ord for BTreeSet<T> where
    T: Ord
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impl<T> Ord for LinkedList<T> where
    T: Ord
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impl<T> Ord for PhantomData<T> where
    T: ?Sized
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impl<T> Ord for ManuallyDrop<T> where
    T: Ord + ?Sized
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impl<T> Ord for Wrapping<T> where
    T: Ord
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impl<T> Ord for NonNull<T> where
    T: ?Sized
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impl<T> Ord for Rc<T> where
    T: Ord + ?Sized
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Comparison for two Rcs.

The two are compared by calling cmp() on their inner values.

Examples

use std::rc::Rc;
use std::cmp::Ordering;

let five = Rc::new(5);

assert_eq!(Ordering::Less, five.cmp(&Rc::new(6)));Run

impl<T> Ord for Arc<T> where
    T: Ord + ?Sized
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Comparison for two Arcs.

The two are compared by calling cmp() on their inner values.

Examples

use std::sync::Arc;
use std::cmp::Ordering;

let five = Arc::new(5);

assert_eq!(Ordering::Less, five.cmp(&Arc::new(6)));Run

impl<T> Ord for Vec<T> where
    T: Ord
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Implements ordering of vectors, lexicographically.

impl<T, E> Ord for Result<T, E> where
    E: Ord,
    T: Ord
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impl<Y, R> Ord for GeneratorState<Y, R> where
    R: Ord,
    Y: Ord
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