March 2014 update

Task/Entropy/Rust/entropy.rust

@@ -0,0 +1,16 @@
+// works for Rust 0.9
+fn entropy(s: &str) -> f32 {
+	let mut entropy: f32 = 0.0;
+	let mut histogram = [0, ..256];
+	let len = s.len();
+
+	for i in range(0, len) { histogram[s[i]] += 1; }
+	for i in range(0, 256) {
+		if histogram[i] > 0 {
+			let ratio = (histogram[i] as f32 / len as f32) as f32;
+			entropy -= (ratio * log2(ratio)) as f32;
+		}
+	}
+
+	entropy
+}