# `superset_map`
`superset_map` is a library for [`Set`](https://docs.rs/zfc/latest/zfc/trait.Set.html)s that have an order defined on them.
Its main data structure is [`SupersetMap`](https://docs.rs/superset_map/latest/superset_map/struct.SupersetMap.html)
which is a specialized version of [`BTreeMap`](https://doc.rust-lang.org/alloc/collections/btree_map/struct.BTreeMap.html)
where only supersets are stored. This can be useful when the keys don't fit well or at all with the concept of
[`RangeBounds`](https://doc.rust-lang.org/stable/core/ops/trait.RangeBounds.html).
## Example
```rust
use core::borrow::Borrow;
use core::cmp::Ordering;
use num_bigint::BigUint;
use superset_map::{SetOrd, SupersetSet};
use zfc::{BoundedCardinality, Cardinality, Set};
#[derive(Clone, Copy, Eq, PartialEq)]
struct ShortAscii<'a> {
val: &'a [u8],
}
impl<'a> ShortAscii<'a> {
fn new(val: &'a [u8]) -> Option<ShortAscii<'a>> {
(val.len() <= 255 && val.is_ascii()).then_some(Self { val })
}
fn len(self) -> u8 {
self.val.len().try_into().expect("The ShortAscii instance was not constructed properly and contains more than 255 bytes.")
}
}
#[derive(Clone, Copy, Eq, PartialEq)]
enum WildcardAscii<'a> {
Plain(ShortAscii<'a>),
// Represents a ShortAscii<'a> with an implicit wildcard at the end
// meaning it's all ShortAscii<'a>s that begin with the contained ShortAscii<'a>.val.
Wildcard(ShortAscii<'a>),
}
impl<'a> WildcardAscii<'a> {
const fn val(self) -> ShortAscii<'a> {
match self {
WildcardAscii::Plain(s) | WildcardAscii::Wildcard(s) => s,
}
}
const fn is_plain(self) -> bool {
match self {
WildcardAscii::Plain(_) => true,
WildcardAscii::Wildcard(_) => false,
}
}
const fn is_wildcard(self) -> bool {
!self.is_plain()
}
}
impl<'a> PartialOrd<Self> for WildcardAscii<'a> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl<'a> Ord for WildcardAscii<'a> {
fn cmp(&self, other: &Self) -> Ordering {
let len = u8::min(self.val().len(), other.val().len()) as usize;
match self.val().val[..len].cmp(&other.val().val[..len]) {
Ordering::Less => Ordering::Less,
Ordering::Equal => {
if self.is_wildcard() {
if other.is_wildcard() {
self.val().len().cmp(&other.val().len()).reverse()
} else {
Ordering::Greater
}
} else if other.is_wildcard() {
Ordering::Less
} else {
self.val().len().cmp(&other.val().len())
}
}
Ordering::Greater => Ordering::Greater,
}
}
}
impl<'a> Set for WildcardAscii<'a> {
type Elem = ShortAscii<'a>;
fn bounded_cardinality(&self) -> BoundedCardinality {
BoundedCardinality::new_exact(self.cardinality().unwrap())
}
fn cardinality(&self) -> Option<Cardinality> {
Some(Cardinality::Finite(match *self {
WildcardAscii::Plain(_) => BigUint::new(vec![1]),
// Geometric series.
WildcardAscii::Wildcard(v) => {
(BigUint::new(vec![128]).pow((u8::MAX - v.len()) as u32 + 1)
- BigUint::new(vec![1]))
/ BigUint::new(vec![127])
}
}))
}
fn contains<Q>(&self, elem: &Q) -> bool
where
Q: Borrow<Self::Elem> + Eq + ?Sized,
{
match *self {
WildcardAscii::Plain(v) => v == *elem.borrow(),
WildcardAscii::Wildcard(v) => {
v.len() <= elem.borrow().len() && *v.val == elem.borrow().val[..v.len() as usize]
}
}
}
fn is_proper_subset(&self, val: &Self) -> bool {
val.is_wildcard()
&& match val.val().len().cmp(&self.val().len()) {
Ordering::Less => val.val().val == &self.val().val[..val.val().len() as usize],
Ordering::Equal => self.is_plain() && self.val() == val.val(),
Ordering::Greater => false,
}
}
fn is_subset(&self, val: &Self) -> bool {
self == val || self.is_proper_subset(val)
}
}
impl<'a> SetOrd for WildcardAscii<'a> {}
fn main() {
let mut set = SupersetSet::new();
set.insert(WildcardAscii::Plain(ShortAscii::new(b"foo").unwrap()));
set.insert(WildcardAscii::Plain(ShortAscii::new(b"bar").unwrap()));
set.insert(WildcardAscii::Wildcard(ShortAscii::new(b"b").unwrap()));
set.insert(WildcardAscii::Wildcard(ShortAscii::new(b"bar").unwrap()));
let mut iter = set.into_iter();
assert!(iter.next().map_or(false, |s| s
== WildcardAscii::Wildcard(ShortAscii::new(b"b").unwrap())));
assert!(iter.next().map_or(false, |s| s
== WildcardAscii::Plain(ShortAscii::new(b"foo").unwrap())));
assert!(iter.next().is_none());
}
```
### Status
This package will be actively maintained until it is deemed “feature complete”.
The crates are only tested on the `x86_64-unknown-linux-gnu` and `x86_64-unknown-openbsd` targets, but
they should work on any [Tier 1 with Host Tools](https://doc.rust-lang.org/beta/rustc/platform-support.html)
target.
Version `1.69.0` or newer of nightly `rustc` is required. Once
[`BTreeMap` cursors are stabilized](https://github.com/rust-lang/rust/issues/107540), stable `rustc` will work.