Added a rust version of the monte carlo example

chapters/monte_carlo/code/rust/monte_carlo.rs

@@ -0,0 +1,30 @@
+// Submitted by jess 3jane
+
+extern crate rand;
+
+use std::f64::consts::PI;
+
+fn in_circle(x: f64, y: f64, radius: f64) -> bool {
+    x * x + y * y < radius * radius
+}
+
+fn monte_carlo(n: i64) -> f64 {
+    let mut count = 0;
+
+    for _ in 0..n {
+        let x = rand::random();
+        let y = rand::random();
+        if in_circle(x, y, 1.0) {
+            count += 1;
+        }
+    }
+
+    // return our pi estimate
+    (4 * count) as f64 / n as f64
+}
+
+fn main() {
+    let pi_estimate = monte_carlo(10000000);
+
+    println!("Percent error is {:.3}%", (100.0 * (PI - pi_estimate) / PI));
+}

chapters/monte_carlo/monte_carlo.md

@@ -78,6 +78,9 @@ Feel free to submit your version via pull request, and thanks for reading!
 {% sample lang="hs" %}
 ### Haskell
 [import, lang:"haskell"](code/haskell/monteCarlo.hs)
+{%sample lang="rs" %}
+### Rust
+[import, lang:"rust"](code/rust/monte_carlo.rs)
 {% endmethod %}