diff --git a/argus-core/src/prelude.rs b/argus-core/src/prelude.rs
index 2b12a41..8a33116 100644
--- a/argus-core/src/prelude.rs
+++ b/argus-core/src/prelude.rs
@@ -1,3 +1,7 @@
 pub use crate::expr::{BoolExpr, Expr, ExprBuilder, ExprRef, NumExpr};
+pub use crate::signals::bool_ops::*;
+pub use crate::signals::cast::*;
+pub use crate::signals::cmp_ops::*;
+pub use crate::signals::num_ops::*;
 pub use crate::signals::Signal;
 pub use crate::{ArgusError, ArgusResult};
diff --git a/argus-core/src/signals.rs b/argus-core/src/signals.rs
index e3d3e2d..d1e1abe 100644
--- a/argus-core/src/signals.rs
+++ b/argus-core/src/signals.rs
@@ -24,7 +24,7 @@ pub use cast::*;
 pub use cmp_ops::*;
 use itertools::Itertools;
 pub use num_ops::*;
-use num_traits::NumCast;
+use num_traits::{Num, NumCast};
 pub use traits::*;
 use utils::intersect_bounds;
 
@@ -396,6 +396,16 @@ impl<T> Signal<T> {
     }
 }
 
+impl<T: Num> Signal<T> {
+    pub fn zero() -> Self {
+        Signal::constant(T::zero())
+    }
+
+    pub fn one() -> Self {
+        Signal::constant(T::one())
+    }
+}
+
 #[cfg(any(test, feature = "arbitrary"))]
 pub mod arbitrary {
     use proptest::prelude::*;
diff --git a/argus-core/src/signals/cmp_ops.rs b/argus-core/src/signals/cmp_ops.rs
index 5b79853..3732bf5 100644
--- a/argus-core/src/signals/cmp_ops.rs
+++ b/argus-core/src/signals/cmp_ops.rs
@@ -20,15 +20,16 @@ where
         // added to the signal appropriately.
         // the union of the sample points in self and other
         let sync_points = self.sync_with_intersection(other)?;
-        let sig: Signal<bool> = sync_points
+        let sig: Option<Signal<bool>> = sync_points
             .into_iter()
             .map(|t| {
                 let lhs = self.interpolate_at(t, Linear).unwrap();
                 let rhs = other.interpolate_at(t, Linear).unwrap();
-                (t, op(lhs.partial_cmp(&rhs).unwrap()))
+                let cmp = lhs.partial_cmp(&rhs);
+                cmp.map(|v| (t, op(v)))
             })
             .collect();
-        Some(sig)
+        sig
     }
 }