Trait konst::cmp::ConstCmp

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pub trait ConstCmp {
    type Kind;
}
Expand description

Marker trait for types that implement the const comparison methods.

§Implementors

Types that implement this trait are also expected to implement at least one of these inherent methods:

use std::cmp::Ordering;

const fn const_eq(&self, other: &Self) -> bool

const fn const_cmp(&self, other: &Self) -> Ordering

§Coercions

The Kind associated type is used in the IsAConstCmp marker type to automatically wrap types in CmpWrapper if they’re from the standard library, otherwise leaving them unwrapped.

§Example

§Manual Implementation

use konst::{
    cmp::{ConstCmp, IsNotStdKind},
    const_cmp, const_eq, try_equal,
};

use std::cmp::Ordering;


struct MyType {
    x: &'static str,
    y: &'static [u16],
}

impl ConstCmp for MyType {
    type Kind = IsNotStdKind;
}

impl MyType {
    pub const fn const_eq(&self, other: &Self) -> bool {
        const_eq!(self.x, other.x) &&
        const_eq!(self.y, other.y)
    }

    pub const fn const_cmp(&self, other: &Self) -> Ordering {
        try_equal!(const_cmp!(self.x, other.x));
        try_equal!(const_cmp!(self.y, other.y))
    }
}

const _: () = {
    let foo = MyType{x: "hello", y: &[3, 5, 8, 13]};
    let bar = MyType{x: "world", y: &[3, 5, 8, 13]};

    assert!(matches!(const_cmp!(foo, foo), Ordering::Equal));
    assert!(matches!(const_cmp!(foo, bar), Ordering::Less));
    assert!(matches!(const_cmp!(bar, foo), Ordering::Greater));
    assert!(const_eq!(foo, foo));
    assert!(!const_eq!(foo, bar));
};

§ìmpl_cmp-based Implementation

You can use impl_cmp to implement this trait, as well as define the same methods for multiple implementations with different type arguments.

use konst::{const_cmp, const_eq, impl_cmp, try_equal};

use std::cmp::Ordering;


struct MyType<'a, T> {
    x: &'a str,
    y: &'a [T],
}

impl_cmp!{
    // The comparison functions are only implemented for these types.
    impl['a] MyType<'a, bool>;
    impl['a] MyType<'a, u16>;
    impl['a] MyType<'a, &'static str>;

    pub const fn const_eq(&self, other: &Self) -> bool {
        const_eq!(self.x, other.x) &&
        const_eq!(self.y, other.y)
    }

    pub const fn const_cmp(&self, other: &Self) -> Ordering {
        try_equal!(const_cmp!(self.x, other.x));
        try_equal!(const_cmp!(self.y, other.y))
    }
}

const _: () = {
    let foo = MyType{x: "hello", y: &[3, 5, 8, 13]};
    let bar = MyType{x: "world", y: &[3, 5, 8, 13]};

    assert!(matches!(const_cmp!(foo, foo), Ordering::Equal));
    assert!(matches!(const_cmp!(foo, bar), Ordering::Less));
    assert!(matches!(const_cmp!(bar, foo), Ordering::Greater));
    assert!(const_eq!(foo, foo));
    assert!(!const_eq!(foo, bar));
};

const _: () = {
    let foo = MyType{x: "hello", y: &[false]};
    let bar = MyType{x: "hello", y: &[true]};

    assert!(matches!(const_cmp!(foo, foo), Ordering::Equal));
    assert!(matches!(const_cmp!(foo, bar), Ordering::Less));
    assert!(matches!(const_cmp!(bar, foo), Ordering::Greater));
    assert!(const_eq!(foo, foo));
    assert!(!const_eq!(foo, bar));
};

Required Associated Types§

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type Kind

What kind of type this is, this can be one of:

Implementations on Foreign Types§

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impl ConstCmp for Ordering

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impl ConstCmp for Option<Ordering>

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impl ConstCmp for Option<bool>

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impl ConstCmp for Option<char>

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impl ConstCmp for Option<i8>

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impl ConstCmp for Option<i16>

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impl ConstCmp for Option<i32>

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impl ConstCmp for Option<i64>

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impl ConstCmp for Option<i128>

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impl ConstCmp for Option<isize>

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impl ConstCmp for Option<u8>

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impl ConstCmp for Option<u16>

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impl ConstCmp for Option<u32>

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impl ConstCmp for Option<u64>

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impl ConstCmp for Option<u128>

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impl ConstCmp for Option<usize>

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impl ConstCmp for Option<NonZeroI8>

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impl ConstCmp for Option<NonZeroI16>

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impl ConstCmp for Option<NonZeroI32>

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impl ConstCmp for Option<NonZeroI64>

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impl ConstCmp for Option<NonZeroI128>

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impl ConstCmp for Option<NonZeroIsize>

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impl ConstCmp for Option<NonZeroU8>

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impl ConstCmp for Option<NonZeroU16>

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impl ConstCmp for Option<NonZeroU32>

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impl ConstCmp for Option<NonZeroU64>

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impl ConstCmp for Option<NonZeroU128>

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impl ConstCmp for Option<NonZeroUsize>

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impl ConstCmp for bool

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impl ConstCmp for char

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impl ConstCmp for i8

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impl ConstCmp for i16

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impl ConstCmp for i32

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impl ConstCmp for i64

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impl ConstCmp for i128

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impl ConstCmp for isize

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impl ConstCmp for str

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impl ConstCmp for u8

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impl ConstCmp for u16

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impl ConstCmp for u32

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impl ConstCmp for u64

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impl ConstCmp for u128

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impl ConstCmp for usize

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impl ConstCmp for PhantomPinned

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impl ConstCmp for Range<char>

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impl ConstCmp for Range<u8>

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impl ConstCmp for Range<u16>

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impl ConstCmp for Range<u32>

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impl ConstCmp for Range<u64>

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impl ConstCmp for Range<u128>

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impl ConstCmp for Range<usize>

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impl ConstCmp for RangeInclusive<char>

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impl ConstCmp for RangeInclusive<u8>

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impl ConstCmp for RangeInclusive<u16>

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impl ConstCmp for RangeInclusive<u32>

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impl ConstCmp for RangeInclusive<u64>

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impl ConstCmp for RangeInclusive<u128>

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impl ConstCmp for RangeInclusive<usize>

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impl ConstCmp for NonZeroI8

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impl ConstCmp for NonZeroI16

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impl ConstCmp for NonZeroI32

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impl ConstCmp for NonZeroI64

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impl ConstCmp for NonZeroI128

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impl ConstCmp for NonZeroIsize

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impl ConstCmp for NonZeroU8

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impl ConstCmp for NonZeroU16

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impl ConstCmp for NonZeroU32

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impl ConstCmp for NonZeroU64

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impl ConstCmp for NonZeroU128

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impl ConstCmp for NonZeroUsize

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impl<'a> ConstCmp for Option<&'a str>

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impl<'a> ConstCmp for Option<&'a [bool]>

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impl<'a> ConstCmp for Option<&'a [char]>

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impl<'a> ConstCmp for Option<&'a [i8]>

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impl<'a> ConstCmp for Option<&'a [i16]>

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impl<'a> ConstCmp for Option<&'a [i32]>

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impl<'a> ConstCmp for Option<&'a [i64]>

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impl<'a> ConstCmp for Option<&'a [i128]>

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impl<'a> ConstCmp for Option<&'a [isize]>

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impl<'a> ConstCmp for Option<&'a [u8]>

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impl<'a> ConstCmp for Option<&'a [u16]>

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impl<'a> ConstCmp for Option<&'a [u32]>

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impl<'a> ConstCmp for Option<&'a [u64]>

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impl<'a> ConstCmp for Option<&'a [u128]>

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impl<'a> ConstCmp for Option<&'a [usize]>

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impl<'a, 'b> ConstCmp for Option<&'a [&'b str]>

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impl<'a, 'b> ConstCmp for Option<&'a [&'b [u8]]>

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impl<T> ConstCmp for &T
where T: ?Sized + ConstCmp,

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impl<T> ConstCmp for &mut T
where T: ?Sized + ConstCmp,

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impl<T> ConstCmp for [T]

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impl<T> ConstCmp for PhantomData<T>

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impl<T, const N: usize> ConstCmp for [T; N]

Implementors§