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use std::{collections::BTreeSet, convert::TryInto};
// From 1.50 std::core::iter::range lines 425--450
fn step_char_forward(c : char) -> Option<char> {
let start = u32::from(c);
let mut res = start.checked_add(1)?;
if start < 0xD800 && 0xD800 <= res {
res = start.checked_add(0x800)?;
}
res.try_into().ok()
}
fn step_char_backward(c : char) -> Option<char> {
let start = u32::from(c);
let mut res = start.checked_sub(1)?;
if start >= 0xE000 && 0xE000 > res {
res = start.checked_sub(0x800)?;
}
res.try_into().ok()
}
#[derive(Clone, Debug, Default, Eq, PartialEq, Hash)]
pub struct FirstSet {
inner: Vec<(char, char)>,
}
impl FirstSet {
pub fn new() -> Self {
Self::default()
}
pub fn of_str(s: &str) -> Self {
Self {
inner: s.chars().next().into_iter().map(|c| (c, c)).collect(),
}
}
pub fn is_empty(&self) -> bool {
self.inner.is_empty()
}
pub fn union(self, mut other: Self) -> Self {
let mut out = Vec::new();
let mut iters = [self.into_iter().peekable(), other.into_iter().peekable()];
'outer: loop {
// Look at the next two ranges, and find the minimum next character
let (min, mut max) = match (iters[0].peek(), iters[1].peek()) {
// Both inputs exhausted
(None, None) => break,
// Add remainder to output
(None, Some(_)) => {
out.extend(iters[1]);
break
}
(Some(_), None) => {
out.extend(iters[0]);
break
}
// The interesting case
(Some((left, left_max)), Some((right, right_max))) => {
if left > right {
iters.swap(0, 1);
(*right, *right_max)
} else {
(*left, *left_max)
}
}
};
max = match step_char_forward(max) {
Some(c) => c,
None => {
// assert!(max == char::MAX)
// This swallows all other ranges
out.push((min, max));
break;
}
};
// There are a few cases:
// - No overlap:
// ----
// ----
// - Extend:
// ----
// ----
// - Swallow:
// ---------
// ----
// We loop until there is no overlap.
// For extend, we step the left and swap.
// For swallow, we step the right only
while let Some((other_min, other_max)) = iters[1].peek() {
if *other_min > max {
// No overlap
break;
}
// max is one past range, other_max is in range, so we use >=
if *other_max >= max {
// Extend
iters[0].next();
iters.swap(0, 1);
max = match step_char_forward(*other_max) {
Some(c) => c,
None => { out.push((min, max)); break 'outer }
};
} else {
// Swallow
iters[1].next();
}
}
let end = step_char_backward(max).expect("char + 1 - 1 != char");
out.push((min, end));
iters[0].next();
}
Self {inner: out}
}
pub fn intersect(&self, other: &Self) -> Self {
todo!()
// Self {
// inner: self.inner.intersection(&other.inner).copied().collect(),
// }
}
}
impl IntoIterator for FirstSet {
type Item = (char, char);
type IntoIter = <Vec<(char, char)> as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.inner.into_iter()
}
}
#[derive(Clone, Debug, Default, Eq, PartialEq, Hash)]
pub struct FlastSet {
inner: BTreeSet<char>,
}
impl FlastSet {
pub fn new() -> Self {
Self::default()
}
pub fn is_empty(&self) -> bool {
self.inner.is_empty()
}
pub fn union_first(mut self, mut other: FirstSet) -> Self {
// self.inner.append(&mut other.inner);
// self
todo!()
}
pub fn union(mut self, mut other: Self) -> Self {
self.inner.append(&mut other.inner);
self
}
pub fn intersect_first(&self, other: &FirstSet) -> Self {
// Self {
// inner: self.inner.intersection(&other.inner).copied().collect(),
// }
todo!()
}
pub fn intersect(&self, other: &Self) -> Self {
Self {
inner: self.inner.intersection(&other.inner).copied().collect(),
}
}
}
impl IntoIterator for FlastSet {
type Item = char;
type IntoIter = <BTreeSet<char> as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.inner.into_iter()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_first_union_none() {
let left = FirstSet { inner: vec![('A', 'Z'), ('a', 'z')]};
let right = FirstSet {inner: vec![]};
assert_eq!(left.union(right), left)
}
#[test]
fn test_first_union_shallow() {
let left = FirstSet { inner: vec![('A', 'Z'), ('a', 'z')]};
let right = FirstSet {inner: vec![('b', 'y')]};
assert_eq!(left.union(right), left)
}
#[test]
fn test_first_union_extend() {
let left = FirstSet { inner: vec![('A', 'Z'), ('a', 'z')]};
let right = FirstSet {inner: vec![('[', '`')]};
assert_eq!(left.union(right), FirstSet {inner: vec![('A', 'z')]})
}
}
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