Implement and test CliffScorer

src/cliff_scorer.rs

@@ -1,8 +1,16 @@
-use ec_core::{individual::scorer::Scorer, test_results::Score};
+use ec_core::individual::scorer::Scorer;
 use ec_linear::genome::bitstring::Bitstring;
 
 use crate::knapsack::Knapsack;
 
+#[derive(Debug, PartialEq, Eq)]
+enum CliffScore {
+    Score(u64),
+    Overloaded,
+}
+
+// We'll need to impl `PartialOrd` and `Ord` on `CliffScore`.
+
 struct CliffScorer {
     knapsack: Knapsack,
 }
@@ -14,9 +22,53 @@ impl CliffScorer {
 }
 
 impl Scorer<Bitstring> for CliffScorer {
-    type Score = anyhow::Result<Score<i64>>;
+    type Score = CliffScore;
 
     fn score(&self, genome: &Bitstring) -> Self::Score {
-        todo!()
+        let value = self.knapsack.value(genome);
+        let weight = self.knapsack.weight(genome);
+        if weight > self.knapsack.capacity() {
+            CliffScore::Overloaded
+        } else {
+            CliffScore::Score(value)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use test_case::test_case;
+
+    use ec_core::individual::scorer::Scorer;
+    use ec_linear::genome::bitstring::Bitstring;
+
+    use crate::{cliff_scorer::CliffScore, item::Item, knapsack::Knapsack};
+
+    use super::CliffScorer;
+
+    #[test_case([false, false, false], 0; "choose no items")]
+    #[test_case([false, true, false], 9; "choose one item")]
+    #[test_case([true, false, true], 7; "choose two items")]
+    fn test_choices(choices: [bool; 3], expected_value: u64) {
+        let knapsack = Knapsack::new(
+            vec![Item::new(1, 5, 8), Item::new(2, 9, 6), Item::new(3, 2, 7)],
+            100,
+        );
+        let scorer = CliffScorer::new(knapsack);
+
+        let choices = Bitstring::from_iter(choices);
+        assert_eq!(scorer.score(&choices), CliffScore::Score(expected_value));
+    }
+
+    #[test]
+    fn test_overloading() {
+        let knapsack = Knapsack::new(
+            vec![Item::new(1, 5, 8), Item::new(2, 9, 6), Item::new(3, 2, 7)],
+            10,
+        );
+        let scorer = CliffScorer::new(knapsack);
+
+        let choices = Bitstring::from_iter([true, true, false]);
+        assert_eq!(scorer.score(&choices), CliffScore::Overloaded);
     }
 }