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

src/history.rs

@@ -1,25 +1,27 @@
 use std::collections::HashMap;
 
 use crate::{
+    BETA, GAMMA, Index, MU, N_INF, P_DRAW, SIGMA,
     agent::{self, Agent},
     batch::{self, Batch},
+    drift::{ConstantDrift, Drift},
     gaussian::Gaussian,
     player::Player,
-    sort_time, tuple_gt, tuple_max, Index, BETA, GAMMA, MU, P_DRAW, SIGMA,
+    sort_time, tuple_gt, tuple_max,
 };
 
 #[derive(Clone)]
-pub struct HistoryBuilder {
+pub struct HistoryBuilder<D: Drift = ConstantDrift> {
     time: bool,
     mu: f64,
     sigma: f64,
     beta: f64,
-    gamma: f64,
+    drift: D,
     p_draw: f64,
     online: bool,
 }
 
-impl HistoryBuilder {
+impl<D: Drift> HistoryBuilder<D> {
     pub fn time(mut self, time: bool) -> Self {
         self.time = time;
         self
@@ -40,9 +42,16 @@ impl HistoryBuilder {
         self
     }
 
-    pub fn gamma(mut self, gamma: f64) -> Self {
-        self.gamma = gamma;
-        self
+    pub fn drift<D2: Drift>(self, drift: D2) -> HistoryBuilder<D2> {
+        HistoryBuilder {
+            drift,
+            time: self.time,
+            mu: self.mu,
+            sigma: self.sigma,
+            beta: self.beta,
+            p_draw: self.p_draw,
+            online: self.online,
+        }
     }
 
     pub fn p_draw(mut self, p_draw: f64) -> Self {
@@ -55,7 +64,7 @@ impl HistoryBuilder {
         self
     }
 
-    pub fn build(self) -> History {
+    pub fn build(self) -> History<D> {
         History {
             size: 0,
             batches: Vec::new(),
@@ -64,41 +73,48 @@ impl HistoryBuilder {
             mu: self.mu,
             sigma: self.sigma,
             beta: self.beta,
-            gamma: self.gamma,
+            drift: self.drift,
             p_draw: self.p_draw,
             online: self.online,
         }
     }
 }
 
-impl Default for HistoryBuilder {
+impl HistoryBuilder<ConstantDrift> {
+    pub fn gamma(mut self, gamma: f64) -> Self {
+        self.drift = ConstantDrift(gamma);
+        self
+    }
+}
+
+impl Default for HistoryBuilder<ConstantDrift> {
     fn default() -> Self {
         Self {
             time: true,
             mu: MU,
             sigma: SIGMA,
             beta: BETA,
-            gamma: GAMMA,
+            drift: ConstantDrift(GAMMA),
             p_draw: P_DRAW,
             online: false,
         }
     }
 }
 
-pub struct History {
+pub struct History<D: Drift = ConstantDrift> {
     size: usize,
     pub(crate) batches: Vec<Batch>,
-    agents: HashMap<Index, Agent>,
+    agents: HashMap<Index, Agent<D>>,
     time: bool,
     mu: f64,
     sigma: f64,
     beta: f64,
-    gamma: f64,
+    drift: D,
     p_draw: f64,
     online: bool,
 }
 
-impl Default for History {
+impl Default for History<ConstantDrift> {
     fn default() -> Self {
         Self {
             size: 0,
@@ -108,18 +124,20 @@ impl Default for History {
             mu: MU,
             sigma: SIGMA,
             beta: BETA,
-            gamma: GAMMA,
+            drift: ConstantDrift(GAMMA),
             p_draw: P_DRAW,
             online: false,
         }
     }
 }
 
-impl History {
-    pub fn builder() -> HistoryBuilder {
+impl History<ConstantDrift> {
+    pub fn builder() -> HistoryBuilder<ConstantDrift> {
         HistoryBuilder::default()
     }
+}
 
+impl<D: Drift> History<D> {
     fn iteration(&mut self) -> (f64, f64) {
         let mut step = (0.0, 0.0);
 
@@ -247,7 +265,7 @@ impl History {
         results: Vec<Vec<f64>>,
         times: Vec<i64>,
         weights: Vec<Vec<Vec<f64>>>,
-        mut priors: HashMap<Index, Player>,
+        mut priors: HashMap<Index, Player<D>>,
     ) {
         assert!(times.is_empty() || self.time, "length(times)>0 but !h.time");
         assert!(
@@ -286,10 +304,11 @@ impl History {
                             Player::new(
                                 Gaussian::from_ms(self.mu, self.sigma),
                                 self.beta,
-                                self.gamma,
+                                self.drift,
                             )
                         }),
-                        ..Default::default()
+                        message: N_INF,
+                        last_time: i64::MIN,
                     },
                 );
             }
@@ -414,7 +433,7 @@ impl History {
 mod tests {
     use approx::assert_ulps_eq;
 
-    use crate::{Game, Gaussian, IndexMap, Player, EPSILON, ITERATIONS, P_DRAW};
+    use crate::{ConstantDrift, EPSILON, Game, Gaussian, ITERATIONS, IndexMap, P_DRAW, Player};
 
     use super::*;
 
@@ -441,7 +460,7 @@ mod tests {
                 Player::new(
                     Gaussian::from_ms(25.0, 25.0 / 3.0),
                     25.0 / 6.0,
-                    0.15 * 25.0 / 3.0,
+                    ConstantDrift(0.15 * 25.0 / 3.0),
                 ),
             );
         }
@@ -503,7 +522,7 @@ mod tests {
                 Player::new(
                     Gaussian::from_ms(25.0, 25.0 / 3.0),
                     25.0 / 6.0,
-                    0.15 * 25.0 / 3.0,
+                    ConstantDrift(0.15 * 25.0 / 3.0),
                 ),
             );
         }
@@ -552,7 +571,7 @@ mod tests {
                 Player::new(
                     Gaussian::from_ms(25.0, 25.0 / 3.0),
                     25.0 / 6.0,
-                    25.0 / 300.0,
+                    ConstantDrift(25.0 / 300.0),
                 ),
             );
         }
@@ -610,7 +629,7 @@ mod tests {
                 Player::new(
                     Gaussian::from_ms(25.0, 25.0 / 3.0),
                     25.0 / 6.0,
-                    25.0 / 300.0,
+                    ConstantDrift(25.0 / 300.0),
                 ),
             );
         }