Trait cantor::Finite

pub unsafe trait Finite: Ord + Clone + Sized {
    const COUNT: usize;

    fn index_of(value: Self) -> usize;
    fn nth(index: usize) -> Option<Self>;

    fn iter() -> FiniteIter<Self> { ... }
}

Provides the number of values for a type, as well as a 1-to-1 mapping between the subset of integers [0 .. N) and those values. The ordering of integers in this mapping is homomorphic to the ordering of values according to Ord (i.e. T::index_of(a) < T::index_of(b) iff a < b).

This trait may be automatically derived.

Example

use cantor::*;
 
#[derive(Finite, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug)]
enum MyType {
    A,
    B(bool),
    C(bool, bool)
}
 
assert_eq!(MyType::COUNT, 7);
assert_eq!(MyType::index_of(MyType::B(false)), 1);
assert_eq!(MyType::nth(4), Some(MyType::C(false, true)));

Safety

index_of must return an integer less than COUNT. nth must return a non-None value iff it is given an integer less than COUNT.

Required Associated Constants

const COUNT: usize

The number of valid values of this type.

Required Methods

fn index_of(value: Self) -> usize

Gets a unique integer representation for the given value. This defines a 1-to-1 mapping between values of this type and non-negative integers less than Finite::COUNT.

fn nth(index: usize) -> Option<Self>

Gets the value with the given index as returned by Finite::index_of, or returns None if the index is out of bounds.

Provided Methods

fn iter() -> FiniteIter<Self>

Iterates over all of the values of this type.

Implementations on Foreign Types

impl Finite for ()

const COUNT: usize = 1usize

fn index_of(_: Self) -> usize

fn nth(index: usize) -> Option<Self>

impl Finite for bool

const COUNT: usize = 2usize

fn index_of(value: Self) -> usize

fn nth(index: usize) -> Option<Self>

impl Finite for u8

const COUNT: usize = 256usize

fn index_of(value: Self) -> usize

fn nth(index: usize) -> Option<Self>

impl Finite for u16

const COUNT: usize = 65_536usize

fn index_of(value: Self) -> usize

fn nth(index: usize) -> Option<Self>

impl<T: Finite> Finite for Option<T>

const COUNT: usize = 1 + T::COUNT

fn index_of(value: Self) -> usize

fn nth(index: usize) -> Option<Self>

impl<A: Finite, B: Finite> Finite for (A, B)

const COUNT: usize = A::COUNT * B::COUNT

fn index_of(value: Self) -> usize

fn nth(index: usize) -> Option<Self>

Implementors

impl<T: BitmapFinite> Finite for BitmapSet<T>

const COUNT: usize = 1 << T::COUNT

impl<T: CompressFinite> Finite for Compress<T>

const COUNT: usize = T::COUNT