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pub trait Point {
fn dist(&self, other: &Self) -> f64;
#[allow(unused_variables)]
fn dist_lower_bound(&self, other: &Self) -> f64 {
::std::f64::NEG_INFINITY
}
}
pub trait Points {
type Point;
}
pub trait RegionQuery: Points {
type Neighbours: Iterator<Item = (f64, Self::Point)>;
fn neighbours(&self, point: &Self::Point, epsilon: f64) -> Self::Neighbours;
}
pub trait ListPoints: Points {
type AllPoints: Iterator<Item = Self::Point>;
fn all_points(&self) -> Self::AllPoints;
}
use std::ops::Range;
use std::slice::Iter;
use std::iter::Enumerate;
pub struct BruteScan<'a, P: Point + 'a> {
points: &'a [P]
}
impl<'a, P: Point> BruteScan<'a, P> {
pub fn new(p: &'a [P]) -> BruteScan<'a, P> {
BruteScan { points: p }
}
}
impl<'a,P: Point> Points for BruteScan<'a, P> {
type Point = usize;
}
impl<'a,P: Point> ListPoints for BruteScan<'a, P> {
type AllPoints = Range<usize>;
fn all_points(&self) -> Range<usize> {
0..self.points.len()
}
}
impl<'a, P: Point> RegionQuery for BruteScan<'a, P> {
type Neighbours = BruteScanNeighbours<'a, P>;
fn neighbours(&self, point: &usize, eps: f64) -> BruteScanNeighbours<'a, P> {
BruteScanNeighbours {
points: self.points.iter().enumerate(),
point: &self.points[*point],
eps: eps
}
}
}
pub struct BruteScanNeighbours<'a, P: Point + 'a> {
points: Enumerate<Iter<'a, P>>,
point: &'a P,
eps: f64,
}
impl<'a,P: Point> Iterator for BruteScanNeighbours<'a, P> {
type Item = (f64, usize);
fn next(&mut self) -> Option<(f64,usize)> {
let BruteScanNeighbours { ref mut points, ref point, eps } = *self;
points.filter_map(|(i, p)| {
if point.dist_lower_bound(p) <= eps {
let d = point.dist(p);
if d <= eps {
return Some((d, i))
}
};
None
}).next()
}
}
#[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Debug)]
pub struct Euclid<T>(pub T);
pub trait Euclidean {
fn zero() -> Self;
fn add(&mut self, &Self);
fn scale(&mut self, f64);
fn dist2(&self, other: &Self) -> f64;
}
macro_rules! euclidean_points {
($($e: expr),*) => {
$(
impl Point for Euclid<[f64; $e]> {
fn dist(&self, other: &Euclid<[f64; $e]>) -> f64 {
self.dist2(other).sqrt()
}
fn dist_lower_bound(&self, other: &Euclid<[f64; $e]>) -> f64 {
(self.0[0] - other.0[0]).abs()
}
}
impl Euclidean for Euclid<[f64; $e]> {
fn zero() -> Self {
Euclid([0.0; $e])
}
fn add(&mut self, other: &Self) {
for (place, val) in self.0.iter_mut().zip(other.0.iter()) {
*place += *val
}
}
fn scale(&mut self, factor: f64) {
for place in &mut self.0 {
*place *= factor
}
}
fn dist2(&self, other: &Euclid<[f64; $e]>) -> f64 {
self.0.iter().zip(other.0.iter())
.map(|(a, b)| {
let d = *a - *b;
d * d
})
.fold(0.0, |a, b| a + b)
}
}
)*
}
}
euclidean_points!(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn euclid() {
let p1 = Euclid([0.0, 1.0]);
let p2 = Euclid([1.0, 0.0]);
assert!((p1.dist(&p2) - 2f64.sqrt()).abs() < 1e-10);
}
#[test]
fn naive_neigbours() {
let points = [Euclid([0.0]), Euclid([10.0]), Euclid([5.0]), Euclid([2.5])];
let points = BruteScan::new(&points);
type V = Vec<(f64, usize)>;
assert_eq!(points.neighbours(&0, 1.0).collect::<V>(),
[(0.0, 0)]);
assert_eq!(points.neighbours(&0, 3.0).collect::<V>(),
[(0.0, 0), (2.5, 3)]);
assert_eq!(points.neighbours(&1, 3.0).collect::<V>(),
[(0.0, 1)]);
assert_eq!(points.neighbours(&1, 10.0).collect::<V>(),
[(10.0, 0), (0.0, 1), (5.0, 2), (7.5, 3)]);
assert_eq!(points.neighbours(&3, 3.0).collect::<V>(),
[(2.5, 0), (2.5, 2), (0.0, 3)]);
}
}