Add Rust implementation for The Barnsley Fern (#818)

* Add Rust implementation for The Barnsley Fern

* Change operators constants and add Cargo.toml

* Fix bug in matrix multiplication

Co-authored-by: James Schloss <jrs.schloss@gmail.com>

contents/barnsley/barnsley.md

@@ -125,6 +125,8 @@ The biggest differences between the two code implementations is that the Barnsle
 {% method %}
 {% sample lang="jl" %}
 [import, lang:"julia"](code/julia/barnsley.jl)
+{% sample lang="rs" %}
+[import, lang:"rust"](code/rust/src/main.rs)
 {% sample lang="cpp" %}
 [import, lang:"cpp"](code/c++/barnsley.cpp)
 {% sample lang="c" %}
@@ -133,7 +135,6 @@ The biggest differences between the two code implementations is that the Barnsle
 [import, lang:"java"](code/java/Barnsley.java)
 {% sample lang="coco" %}
 [import, lang:"coconut"](code/julia/barnsley.coco)
-
 {% endmethod %}
 
 ### Bibliography

contents/barnsley/code/rust/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "rust"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rand = "0.8.4"

contents/barnsley/code/rust/src/main.rs

@@ -0,0 +1,105 @@
+use rand::prelude::*;
+#[derive(Clone, Copy)]
+struct Point2 {
+    x: f64,
+    y: f64,
+}
+
+#[derive(Clone, Copy)]
+struct Point3 {
+    x: f64,
+    y: f64,
+    z: f64,
+}
+
+impl Point3 {
+    fn new(x: f64, y: f64, z: f64) -> Self {
+        Self { x, y, z }
+    }
+
+    fn matrix_mul(self, rhs: Vec<Point3>) -> Self {
+        let x = rhs[0].x * self.x + rhs[0].y * self.y + rhs[0].z * self.z;
+        let y = rhs[1].x * self.x + rhs[1].y * self.y + rhs[1].z * self.z;
+        let z = rhs[2].x * self.x + rhs[2].y * self.y + rhs[2].z * self.z;
+        Self::new(x, y, z)
+    }
+}
+
+fn select_array(hutchinson_op: &[Vec<Point3>], probabilities: &[f64]) -> Vec<Point3> {
+    let mut rng = rand::thread_rng();
+    let mut rnd = rng.gen::<f64>();
+
+    for (i, probability) in probabilities.iter().enumerate() {
+        if rnd < *probability {
+            return hutchinson_op[i].clone();
+        }
+        rnd -= probability;
+    }
+
+    return vec![];
+}
+
+fn chaos_game(
+    iters: usize,
+    initial_location: Point2,
+    hutchinson_op: &[Vec<Point3>],
+    probabilities: &[f64],
+) -> Vec<Point2> {
+    let mut point = Point3 {
+        x: initial_location.x,
+        y: initial_location.y,
+        z: 1.0,
+    };
+    (0..iters)
+        .into_iter()
+        .map(|_| {
+            let old_point = point;
+            let operation = select_array(hutchinson_op, probabilities);
+            point = point.matrix_mul(operation);
+            Point2 {
+                x: old_point.x,
+                y: old_point.y,
+            }
+        })
+        .collect()
+}
+
+fn main() {
+    let barnsley_hutchinson = vec![
+        vec![
+            Point3::new(0.0, 0.0, 0.0),
+            Point3::new(0.0, 0.16, 0.0),
+            Point3::new(0.0, 0.0, 1.0),
+        ],
+        vec![
+            Point3::new(0.85, 0.04, 0.0),
+            Point3::new(-0.04, 0.85, 1.60),
+            Point3::new(0.0, 0.0, 1.0),
+        ],
+        vec![
+            Point3::new(0.20, -0.26, 0.0),
+            Point3::new(0.23, 0.22, 1.60),
+            Point3::new(0.0, 0.0, 1.0),
+        ],
+        vec![
+            Point3::new(-0.15, 0.28, 0.0),
+            Point3::new(0.26, 0.24, 0.44),
+            Point3::new(0.0, 0.0, 1.0),
+        ],
+    ];
+
+    let barnsley_probabilities = vec![0.01, 0.85, 0.07, 0.07];
+
+    let mut out = String::new();
+
+    for point in chaos_game(
+        10_000,
+        Point2 { x: 0.0, y: 0.0 },
+        &barnsley_hutchinson,
+        &barnsley_probabilities,
+    ) {
+        out += format!("{}\t{}\n", point.x, point.y).as_str();
+    }
+
+    std::fs::write("./out.dat", out).unwrap();
+}