diff -r c5f70e767511 -r f802ddbabcfc src/bisection_tree/either.rs
--- a/src/bisection_tree/either.rs	Tue Dec 31 08:48:50 2024 -0500
+++ b/src/bisection_tree/either.rs	Mon Dec 23 23:27:45 2024 -0500
@@ -9,6 +9,7 @@
     DifferentiableImpl,
     DifferentiableMapping,
     Space,
+    ArithmeticTrue,
 };
 use crate::iter::{Mappable, MapF, MapZ};
 use crate::sets::Cube;
@@ -191,6 +192,7 @@
     S2 : Mapping<X, Codomain=F>,
 {
     type Codomain = F;
+    type ArithmeticOptIn = ArithmeticTrue;
 
     #[inline]
     fn apply<I : Instance<X>>(&self, x : I) -> F {