It works?!

src/gaussian.rs

@@ -1,10 +1,51 @@
+use std::ops;
+
+#[derive(Clone, Copy)]
 pub struct Gaussian {
     pub pi: f32,
     pub tau: f32,
 }
 
 impl Gaussian {
-    pub fn new(pi: f32, tau: f32) -> Gaussian {
+    pub fn new() -> Gaussian {
+        Gaussian::with_pi_tau(0.0, 0.0)
+    }
+
+    pub fn with_pi_tau(pi: f32, tau: f32) -> Gaussian {
         Gaussian { pi, tau }
     }
+
+    pub fn with_mu_sigma(mu: f32, sigma: f32) -> Gaussian {
+        let pi = 1.0 / sigma.powi(2);
+
+        Gaussian::with_pi_tau(pi, pi * mu)
+    }
+
+    pub fn mu(&self) -> f32 {
+        if self.pi == 0.0 {
+            0.0
+        } else {
+            self.tau / self.pi
+        }
+    }
+
+    pub fn sigma(&self) -> f32 {
+        (1.0 / self.pi).sqrt()
+    }
+}
+
+impl ops::Mul<Gaussian> for Gaussian {
+    type Output = Gaussian;
+
+    fn mul(self, rhs: Gaussian) -> Gaussian {
+        Gaussian::with_pi_tau(self.pi + rhs.pi, self.tau + rhs.tau)
+    }
+}
+
+impl ops::Div<Gaussian> for Gaussian {
+    type Output = Gaussian;
+
+    fn div(self, rhs: Gaussian) -> Gaussian {
+        Gaussian::with_pi_tau(self.pi - rhs.pi, self.tau - rhs.tau)
+    }
 }