Add interpolation method for discrete events

argus/src/core/signals/interpolation.rs

@@ -28,6 +28,28 @@ impl<T: Clone> InterpolationMethod<T> for Constant {
     }
 }
 
+/// Fixed Value interpolation.
+///
+/// If the signal does not have a value at a given point, a fixed value is returned
+pub struct DefaultFalse;
+
+impl InterpolationMethod<Bool> for DefaultFalse {
+    fn at(a: &Sample<Bool>, b: &Sample<Bool>, time: Duration) -> Option<Bool> {
+        if time == b.time {
+            Some(b.value.clone())
+        } else if a.time <= time && time < b.time {
+            Some(a.value.clone())
+        } else {
+            Some(false)
+        }
+    }
+
+    fn find_intersection(_a: &Neighborhood<Bool>, _b: &Neighborhood<Bool>) -> Option<Sample<Bool>> {
+        // The signals must be either constant or colinear. Thus, return None.
+        None
+    }
+}
+
 /// Nearest interpolation.
 ///
 /// Here, the signal value from the nearest sample (time-wise) is propagated to the