Koch curve: Difference between revisions

=={{header|Rust}}==

Output is a file in SVG format depicting a Koch snowflake.

<lang rust>// [dependencies]

// svg = "0.8.0"

use svg::node::element::Rectangle;

use svg::node::element::Path;

use svg::node::element::path::Data;

const SQRT3_2 : f64 = 0.86602540378444;

fn koch_curve(mut data: Data, x0 : f64, y0 : f64,

x1 : f64, y1 : f64, order : usize) -> Data {

if order == 0 {

data = data.line_to((x1, y1));

} else {

let dx = x1 - x0;

let dy = y1 - y0;

let x2 = x0 + dx/3.0;

let y2 = y0 + dy/3.0;

let x3 = x0 + dx/2.0 - dy * SQRT3_2/3.0;

let y3 = y0 + dy/2.0 + dx * SQRT3_2/3.0;

let x4 = x0 + 2.0 * dx/3.0;

let y4 = y0 + 2.0 * dy/3.0;

data = koch_curve(data, x0, y0, x2, y2, order - 1);

data = koch_curve(data, x2, y2, x3, y3, order - 1);

data = koch_curve(data, x3, y3, x4, y4, order - 1);

data = koch_curve(data, x4, y4, x1, y1, order - 1);

}

data

}

fn write_koch_snowflake(file : &str, size : usize,

order : usize) -> std::io::Result<()> {

let length = (size as f64) * SQRT3_2 * 0.95;

let x0 = ((size as f64) - length)/2.0;

let y0 = (size as f64)/2.0 - length * SQRT3_2/3.0;

let x1 = x0 + length/2.0;

let y1 = y0 + length * SQRT3_2;

let x2 = x0 + length;

let mut data = Data::new().move_to((x0, y0));

data = koch_curve(data, x0, y0, x1, y1, order);

data = koch_curve(data, x1, y1, x2, y0, order);

data = koch_curve(data, x2, y0, x0, y0, order);

let path = Path::new()

.set("fill", "none")

.set("stroke", "white")

.set("stroke-width", "1")

.set("d", data);

let rect = Rectangle::new()

.set("width", "100%")

.set("height", "100%")

.set("fill", "black");

let document = svg::Document::new()

.set("width", size)

.set("height", size)

.add(rect)

.add(path);

svg::save(file, &document)

}

fn main() {

write_koch_snowflake("koch_snowflake.svg", 600, 5).unwrap();

}</lang>