discrete_range_map

This crate has been renamed to [nodit]

Around 2024-01-03 in release v0.7.0 this crate was renamed from discrete_range_map to nodit due to the old name becoming in-accurate. Please switch to the nodit crate as this crate will no longer be receiving updates.

Old Readme

This crate provides [DiscreteRangeMap] and [DiscreteRangeSet], Data Structures for storing non-overlapping discrete intervals based off BTreeMap.

no_std is supported and should work with the default features.

You must implement Copy

Due to implementation complications with non-Copy types the datastructures currently require both the range type and the points the ranges are over to be Copy.

Example using an Inclusive-Exclusive range

use discrete_range_map::test_ranges::ie;
use discrete_range_map::DiscreteRangeMap;

let mut map = DiscreteRangeMap::new();

map.insert_strict(ie(0, 5), true);
map.insert_strict(ie(5, 10), false);

assert_eq!(map.overlaps(ie(-2, 12)), true);
assert_eq!(map.contains_point(20), false);
assert_eq!(map.contains_point(5), true);

Example using a custom range type

use std::ops::{Bound, RangeBounds};

use discrete_range_map::test_ranges::ie;
use discrete_range_map::{
	DiscreteFinite, DiscreteRangeMap, InclusiveInterval,
	InclusiveRange,
};

#[derive(Debug, Copy, Clone)]
enum Reservation {
	// Start, End (Inclusive-Inclusive)
	Finite(i8, i8),
	// Start (Inclusive-Infinity)
	Infinite(i8),
}

// First, we need to implement InclusiveRange
impl InclusiveRange<i8> for Reservation {
	fn start(&self) -> i8 {
		match self {
			Reservation::Finite(start, _) => *start,
			Reservation::Infinite(start) => *start,
		}
	}
	fn end(&self) -> i8 {
		match self {
			Reservation::Finite(_, end) => *end,
			Reservation::Infinite(_) => i8::MAX,
		}
	}
}

// Second, we need to implement From<InclusiveInterval<i8>>
impl From<InclusiveInterval<i8>> for Reservation {
	fn from(value: InclusiveInterval<i8>) -> Self {
		if value.end == i8::MAX {
			Reservation::Infinite(value.start)
		} else {
			Reservation::Finite(
				value.start,
				value.end.up().unwrap(),
			)
		}
	}
}

// Next we can create a custom typed DiscreteRangeMap
let reservation_map = DiscreteRangeMap::from_slice_strict([
	(Reservation::Finite(10, 20), "Ferris".to_string()),
	(Reservation::Infinite(21), "Corro".to_string()),
])
.unwrap();

for (reservation, name) in reservation_map.overlapping(ie(16, 17))
{
	println!(
		"{name} has reserved {reservation:?} inside the range 16..17"
	);
}

for (reservation, name) in reservation_map.iter() {
	println!("{name} has reserved {reservation:?}");
}

assert_eq!(
	reservation_map.overlaps(Reservation::Infinite(0)),
	true
);

Key Understandings and Philosophies:

Discrete-ness

This crate is designed to work with Discrete types as compared to Continuous types. For example, u8 is a Discrete type, but String is a Continuous if you try to parse it as a decimal value.

The reason for this is that common interval-Mathematics operations differ depending on wether the underlying type is Discrete or Continuous. For example 5..=6 touches 7..=8 since integers are Discrete but 5.0..=6.0 does not touch 7.0..=8.0 since the value 6.5 exists.

Finite-ness

This crate is also designed to work with Finite types since it is much easier to implement and it is not restrictive to users since you can still represent Infinite numbers in Finite types paradoxically using the concept of Actual Infinity.

For example you could define Infinite for u8 as u8::MAX or if you still want to use u8::MAX as a Finite number you could define a wrapper type for u8 that adds an Actual Infinity value to the u8 set.

Invalid Ranges

Within this crate, not all ranges are considered valid ranges. The definition of the validity of a range used within this crate is that a range is only valid if it contains at least one value of the underlying domain.

For example, 4..6 is considered valid as it contains the values 4 and 5, however, 4..4 is considered invalid as it contains no values. Another example of invalid range are those whose start values are greater than their end values. such as 5..2 or 100..=40.

Here are a few examples of ranges and whether they are valid:

Overlap

Two ranges are "overlapping" if there exists a point that is contained within both ranges.

Touching

Two ranges are "touching" if they do not overlap and there exists no value between them. For example, 2..4 and 4..6 are touching but 2..4 and 6..8 are not, neither are 2..6 and 4..8.

Merging

When a range "merges" other ranges it absorbs them to become larger.

Further Reading

See Wikipedia's article on mathematical Intervals: https://en.wikipedia.org/wiki/Interval_(mathematics)

Features

This crate currently has no features.

Credit

I originally came up with the StartBound: Ord bodge on my own, however, I later stumbled across rangemap which also used a StartBound: Ord bodge. rangemap then became my main source of inspiration.

Later I then undid the Ord bodge and switched to my own full-code port of BTreeMap, inspired and forked from copse, for it's increased flexibility.

Origin

The aim for this library was to become a more generic superset of rangemap, following from this issue and this pull request in which I changed rangemap's RangeMap to use RangeBoundss as keys before I realized it might be easier and simpler to just write it all from scratch.

It is however worth noting the library eventually expanded and evolved from it's origins.

This crate was previously named range_bounds_map.

Similar Crates

Here are some relevant crates I found whilst searching around the topic area:

• https://docs.rs/rangemap Very similar to this crate but can only use Ranges and RangeInclusives as keys in it's map and set structs (separately).
• https://docs.rs/btree-range-map
• https://docs.rs/ranges Cool library for fully-generic ranges (unlike std::ops ranges), along with a Ranges datastructure for storing them (Vec-based unfortunately)
• https://docs.rs/intervaltree Allows overlapping intervals but is immutable unfortunately
• https://docs.rs/nonoverlapping_interval_tree Very similar to rangemap except without a gaps() function and only for Ranges and not RangeInclusives. And also no fancy merging functions.
• https://docs.rs/unbounded-interval-tree A data structure based off of a 2007 published paper! It supports any range as keys, unfortunately, it is implemented with a non-balancing Box<Node> based tree, however it also supports overlapping ranges which my library does not.
• https://docs.rs/rangetree I'm not entirely sure what this library is or isn't, but it looks like a custom red-black tree/BTree implementation used specifically for a Range Tree. Interesting but also quite old (5 years) and uses unsafe.

[nodit] https://docs.rs/nodit