Small refactor

src/gaussian.rs

@@ -9,9 +9,7 @@ pub struct Gaussian {
 }
 
 impl Gaussian {
-    pub fn new(mu: f64, sigma: f64) -> Self {
-        debug_assert!(sigma >= 0.0, "sigma must be equal or larger than 0.0");
-
+    pub const fn from_ms(mu: f64, sigma: f64) -> Self {
         Gaussian { mu, sigma }
     }