feat: added a Drift trait and a "default" ConstantDrift implementation

src/agent.rs

@@ -1,23 +1,29 @@
-use crate::{gaussian::Gaussian, player::Player, N_INF};
+use crate::{
+    N_INF,
+    drift::{ConstantDrift, Drift},
+    gaussian::Gaussian,
+    player::Player,
+};
 
 #[derive(Debug)]
-pub struct Agent {
-    pub player: Player,
+pub struct Agent<D: Drift = ConstantDrift> {
+    pub player: Player<D>,
     pub message: Gaussian,
     pub last_time: i64,
 }
 
-impl Agent {
+impl<D: Drift> Agent<D> {
     pub(crate) fn receive(&self, elapsed: i64) -> Gaussian {
         if self.message != N_INF {
-            self.message.forget(self.player.gamma, elapsed)
+            self.message
+                .forget(self.player.drift.variance_delta(elapsed))
         } else {
             self.player.prior
         }
     }
 }
 
-impl Default for Agent {
+impl Default for Agent<ConstantDrift> {
     fn default() -> Self {
         Self {
             player: Player::default(),
@@ -27,7 +33,10 @@ impl Default for Agent {
     }
 }
 
-pub(crate) fn clean<'a, A: Iterator<Item = &'a mut Agent>>(agents: A, last_time: bool) {
+pub(crate) fn clean<'a, D: Drift + 'a, A: Iterator<Item = &'a mut Agent<D>>>(
+    agents: A,
+    last_time: bool,
+) {
     for a in agents {
         a.message = N_INF;