Add an example using Math

examples/math/src/lib.rs

@@ -0,0 +1,26 @@
+#![feature(proc_macro)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern {
+    #[wasm_bindgen(namespace = Math)]
+    fn log2(a: f64) -> f64;
+    #[wasm_bindgen(namespace = Math)]
+    fn sin(a: f64) -> f64;
+
+    #[wasm_bindgen(namespace = console)]
+    fn log(a: &str);
+}
+
+macro_rules! println {
+    ($($t:tt)*) => (console::log(&format_args!($($t)*).to_string()))
+}
+
+#[wasm_bindgen]
+pub fn run() {
+    println!("Math.log2(10.0) = {}", Math::log2(10.0));
+    println!("Math.sin(1.2) = {}", Math::sin(1.2));
+}