Trait counting_sort::TryIntoIndex

pub trait TryIntoIndex {
    type Error;
    fn try_into_index(
        value: &Self, 
        min_value: &Self
    ) -> Result<usize, Self::Error>;
}

The interface for converting values into an index.

Index is always usize. Unfortunatelly TryInto for usize is not sufficient since signed integers overflow when calculating max_value - min_value. Therefore this trait was added to implement an non-overflowing conversion to usize.

You can implement this trait yourself as long as there is a natural conversion from your type to usize. However it must hold for your type that if t_1 <= t_2 then YourType::try_into_index(t_1, min_value)? <= YourType::try_into_index(t_2, min_value)?. Also consider that the size Vec that holds the frequency of all elements in the collection is calculated like this

let length = YourType::try_into_index(max_value,min_value)? + 1;

It is not highly recommended to do this if your type's order is not simply dependent on one integer value of your struct.

Example

use core::cmp::{Ord, Ordering};
use counting_sort::TryIntoIndex;

#[derive(Copy, Clone)]
struct Person {
    name: &'static str,
    id: usize
}

impl Ord for Person {
    fn cmp(&self, other: &Self) -> Ordering {
        self.id.cmp(&other.id)
    }
}

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.id == other.id
    }
}

impl Eq for Person {}

impl TryIntoIndex for Person {
    type Error = &'static str;
     
    fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error> {
        Ok(value.id - min_value.id)
    }
}

let john = Person { name: "John", id: 1234 };
let min_value = Person { name: "Jim", id: 234 };
let index_result = Person::try_into_index(&john, &min_value);
assert!(index_result.is_ok());
assert_eq!(1000, index_result.unwrap_or(0));

Associated Types

type Error

The type returned whenever the conversion into an index failed.

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Required methods

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

Tries to convert the value into an index.

The min_value parameter is for calculating the offset between the actual value and the minimum value. This concept is used in order to only allocate a Vec that only covers the distance between the maximum value and the minimum value of the collection.

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Implementations on Foreign Types

impl TryIntoIndex for i8

type Error = <i16 as TryInto<usize>>::Error

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

impl TryIntoIndex for i16

type Error = <i32 as TryInto<usize>>::Error

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

impl TryIntoIndex for i32

type Error = <i64 as TryInto<usize>>::Error

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

impl TryIntoIndex for u8

type Error = CountingSortError

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

impl TryIntoIndex for u16

type Error = CountingSortError

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

impl TryIntoIndex for u32

type Error = <u32 as TryInto<usize>>::Error

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

impl TryIntoIndex for usize

type Error = <usize as TryInto<usize>>::Error

fn try_into_index(value: &Self, min_value: &Self) -> Result<usize, Self::Error>

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Implementors

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