Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.
use super::funejson::Value; ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
// The latitude/longitude box that contains every point within a distance of a
// centre, by the method of J. P. Matuschek, "Finding Points Within a Distance
// of a Latitude/Longitude Using Bounding Coordinates"
// (http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates).
//
// The trigonometry is written out below instead of calling f64::sin and
// friends, because the platform maths library may differ in the last bit
// between Rust, JavaScript and Python. Only correctly-rounded IEEE 754
// operations (+ - * / sqrt floor) are used, in the same order in all three.
/// IUGG mean radius R1 of the GRS 80 ellipsoid (Moritz, Journal of Geodesy 74 (2000)).
const EARTH_RADIUS_METRES: f64 = 6371008.8;
/// Ten millionths of a degree, about a centimetre.
const SCALE: f64 = 10000000.0;
/// Within a millionth of a grid step of a 7-decimal value counts as that value,
/// so a centre of 51.5074 stays 51.5074 rather than becoming 51.5073999.
const SNAP: f64 = 0.000001;
const PI: f64 = 3.141592653589793;
const HALF_PI: f64 = PI / 2.0;
const DEGREES: f64 = PI / 180.0;
const S3: f64 = -1.0 / 6.0;
const S5: f64 = 1.0 / 120.0;
const S7: f64 = -1.0 / 5040.0;
const S9: f64 = 1.0 / 362880.0;
const S11: f64 = -1.0 / 39916800.0;
const S13: f64 = 1.0 / 6227020800.0;
const S15: f64 = -1.0 / 1307674368000.0;
const S17: f64 = 1.0 / 355687428096000.0;
const C2: f64 = -1.0 / 2.0;
const C4: f64 = 1.0 / 24.0;
const C6: f64 = -1.0 / 720.0;
const C8: f64 = 1.0 / 40320.0;
const C10: f64 = -1.0 / 3628800.0;
const C12: f64 = 1.0 / 479001600.0;
const C14: f64 = -1.0 / 87178291200.0;
const C16: f64 = 1.0 / 20922789888000.0;
const C18: f64 = -1.0 / 6402373705728000.0;
const A3: f64 = -1.0 / 3.0;
const A5: f64 = 1.0 / 5.0;
const A7: f64 = -1.0 / 7.0;
const A9: f64 = 1.0 / 9.0;
const A11: f64 = -1.0 / 11.0;
const A13: f64 = 1.0 / 13.0;
const A15: f64 = -1.0 / 15.0;
const A17: f64 = 1.0 / 17.0;
const A19: f64 = -1.0 / 19.0;
const A21: f64 = 1.0 / 21.0;
fn sin_small(r: f64) -> f64 {
let s = r * r;
let mut p = S17;
p = S15 + s * p;
p = S13 + s * p;
p = S11 + s * p;
p = S9 + s * p;
p = S7 + s * p;
p = S5 + s * p;
p = S3 + s * p;
r + r * s * p
}
fn cos_small(r: f64) -> f64 {
let s = r * r;
let mut p = C18;
p = C16 + s * p;
p = C14 + s * p;
p = C12 + s * p;
p = C10 + s * p;
p = C8 + s * p;
p = C6 + s * p;
p = C4 + s * p;
p = C2 + s * p;
1.0 + s * p
}
fn sin_cos(x: f64) -> (f64, f64) {
let k = (x / HALF_PI + 0.5).floor();
let r = x - k * HALF_PI;
let sr = sin_small(r);
let cr = cos_small(r);
match (k as i64).rem_euclid(4) {
0 => (sr, cr),
1 => (cr, -sr),
2 => (-sr, -cr),
_ => (-cr, sr),
}
}
fn atan_unit(u: f64) -> f64 {
let mut v = u;
v = v / (1.0 + (1.0 + v * v).sqrt());
v = v / (1.0 + (1.0 + v * v).sqrt());
v = v / (1.0 + (1.0 + v * v).sqrt());
let s = v * v;
let mut p = A21;
p = A19 + s * p;
p = A17 + s * p;
p = A15 + s * p;
p = A13 + s * p;
p = A11 + s * p;
p = A9 + s * p;
p = A7 + s * p;
p = A5 + s * p;
p = A3 + s * p;
8.0 * (v + v * s * p)
}
/// asin for 0 <= x, via atan; (1 - x)(1 + x) keeps precision near 1.
fn asin_positive(x: f64) -> f64 {
if x >= 1.0 {
return HALF_PI;
}
let t = x / ((1.0 - x) * (1.0 + x)).sqrt();
if t > 1.0 {
HALF_PI - atan_unit(1.0 / t)
} else {
atan_unit(t)
}
}
/// Outward rounding: a lower bound goes down and an upper bound goes up, so
/// rounding can only grow the box, never cut the circle.
fn round_down(x: f64) -> f64 {
(x * SCALE + SNAP).floor() / SCALE + 0.0
}
fn round_up(x: f64) -> f64 {
(x * SCALE - SNAP).ceil() / SCALE + 0.0
}
fn check_number(value: f64, what: &str) {
if !value.is_finite() {
panic!("{} must be a finite number", what);
}
}
/// The box containing every point within `distance_metres` of (`lat`, `lng`).
///
/// # Panics
/// Panics if a coordinate is out of range or the distance is negative or not finite.
pub fn bounding_box(lat: f64, lng: f64, distance_metres: f64) -> BoundingBox {
check_number(lat, "latitude");
check_number(lng, "longitude");
check_number(distance_metres, "distance");
if lat < -90.0 || lat > 90.0 {
panic!("latitude must be between -90 and 90 degrees");
}
if lng < -180.0 || lng > 180.0 {
panic!("longitude must be between -180 and 180 degrees");
}
if distance_metres < 0.0 {
panic!("distance must be 0 or more metres");
}
let r = distance_metres / EARTH_RADIUS_METRES;
let r_degrees = r / DEGREES;
let mut min_lat = lat - r_degrees;
let mut max_lat = lat + r_degrees;
let mut min_lng;
let mut max_lng;
if min_lat > -90.0 && max_lat < 90.0 {
let sin_r = sin_cos(r).0;
let cos_lat = sin_cos(lat * DEGREES).1;
let d_lng = asin_positive(sin_r / cos_lat) / DEGREES;
min_lng = lng - d_lng;
max_lng = lng + d_lng;
// Past the antimeridian the bound comes round the other side, leaving
// min_lng > max_lng: the box is the two strips either side of 180.
if min_lng < -180.0 {
min_lng += 360.0;
}
if max_lng > 180.0 {
max_lng -= 360.0;
}
} else {
// The circle reaches a pole, so it covers every longitude.
if min_lat < -90.0 {
min_lat = -90.0;
}
if max_lat > 90.0 {
max_lat = 90.0;
}
min_lng = -180.0;
max_lng = 180.0;
}
BoundingBox {
min_lat: round_down(min_lat),
min_lng: round_down(min_lng),
max_lat: round_up(max_lat),
max_lng: round_up(max_lng),
}
}
pub fn bounding_box_to_value(b: &BoundingBox) -> Value {
Value::obj(vec![
("minLat", Value::Float(b.min_lat)),
("minLng", Value::Float(b.min_lng)),
("maxLat", Value::Float(b.max_lat)),
("maxLng", Value::Float(b.max_lng)),
])
}
pub fn fune_vector(args: &[Value]) -> Value {
// Refuse what the typed signature cannot hold, with the wording TypeScript
// and Python use, rather than let the conversion below quietly change it.
if !matches!(args[0], Value::Int(_) | Value::Float(_)) {
panic!("latitude must be a finite number");
}
if !matches!(args[1], Value::Int(_) | Value::Float(_)) {
panic!("longitude must be a finite number");
}
if !matches!(args[2], Value::Int(_) | Value::Float(_)) {
panic!("distance must be a finite number");
}
bounding_box_to_value(&bounding_box(
args[0].as_f64(),
args[1].as_f64(),
args[2].as_f64(),
))
}