superset_map
superset_map is a library for Sets that have an order defined on them.
It's main data structure is SupersetMap
which is a specialized version of BTreeMap
where only supersets are stored. This can be useful when the keys don't fit well or at all with the concept of
RangeBounds.
Example
```rust
use core::borrow::Borrow;
use core::cmp::Ordering;
use numbigint::BigUint;
use supersetmap::{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> {
(val.len() <= 255 && val.isascii()).thensome(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 isplain(self) -> bool {
match self {
WildcardAscii::Plain() => true,
WildcardAscii::Wildcard() => false,
}
}
const fn iswildcard(self) -> bool {
!self.isplain()
}
}
impl<'a> PartialOrd for WildcardAscii<'a> {
fn partialcmp(&self, other: &Self) -> Option {
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.iswildcard() {
if other.iswildcard() {
self.val().len().cmp(&other.val().len()).reverse()
} else {
Ordering::Greater
}
} else if other.iswildcard() {
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 boundedcardinality(&self) -> BoundedCardinality {
BoundedCardinality::newexact(self.cardinality().unwrap())
}
fn cardinality(&self) -> Option {
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(&self, elem: &Q) -> bool
where
Q: Borrow + 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 ispropersubset(&self, val: &Self) -> bool {
val.iswildcard()
&& match val.val().len().cmp(&self.val().len()) {
Ordering::Less => val.val().val == &self.val().val[..val.val().len() as usize],
Ordering::Equal => self.isplain() && self.val() == val.val(),
Ordering::Greater => false,
}
}
fn issubset(&self, val: &Self) -> bool {
self == val || self.ispropersubset(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.intoiter();
assert!(iter.next().mapor(false, |s| s
== WildcardAscii::Wildcard(ShortAscii::new(b"b").unwrap())));
assert!(iter.next().mapor(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
target.
Version 1.69.0 or newer of nightly rustc is required. Once
BTreeMap cursors are stablilized, stable rustc will work.