diff -r cfd8d2304e9e -r 15f01efc034b src/dist.rs
--- a/src/dist.rs	Sat Dec 07 21:54:59 2024 -0500
+++ b/src/dist.rs	Sun Dec 15 01:10:52 2024 -0500
@@ -2,7 +2,7 @@
 Implementations of the distance function and the distance function squared, on manifolds.
 */
 
-use alg_tools::mapping::Apply;
+use alg_tools::mapping::{Mapping, Instance};
 use alg_tools::euclidean::Euclidean;
 use crate::manifold::ManifoldPoint;
 use crate::fb::{Grad, Desc, Prox};
@@ -10,39 +10,22 @@
 /// Structure for distance-to functions
 pub struct DistTo<M : ManifoldPoint>(pub M);
 
-impl<M : ManifoldPoint> Apply<M> for DistTo<M> {
-    type Output = f64;
+impl<M : ManifoldPoint> Mapping<M> for DistTo<M> {
+    type Codomain = f64;
 
-    fn apply(&self, x : M) -> Self::Output {
-        self.0.dist_to(&x)
-    }
-}
-
-impl<'a, M : ManifoldPoint> Apply<&'a M> for DistTo<M> {
-    type Output = f64;
-
-    fn apply(&self, x : &'a M) -> Self::Output {
-        self.0.dist_to(x)
+    fn apply<I : Instance<M>>(&self, x : I) -> Self::Codomain {
+        x.eval(|x̃| self.0.dist_to(x̃))
     }
 }
 
 /// Structure for distance-to functions
 pub struct DistToSquaredDiv2<M : ManifoldPoint>(pub M);
 
-impl<M : ManifoldPoint> Apply<M> for DistToSquaredDiv2<M> {
-    type Output = f64;
+impl<M : ManifoldPoint> Mapping<M> for DistToSquaredDiv2<M> {
+    type Codomain = f64;
 
-    fn apply(&self, x : M) -> Self::Output {
-        let d = self.0.dist_to(&x);
-        d*d / 2.0
-    }
-}
-
-impl<'a, M : ManifoldPoint> Apply<&'a M> for DistToSquaredDiv2<M> {
-    type Output = f64;
-
-    fn apply(&self, x : &'a M) -> Self::Output {
-        let d = self.0.dist_to(x);
+    fn apply<I : Instance<M>>(&self, x : I) -> Self::Codomain {
+        let d = x.eval(|x̃| self.0.dist_to(x̃));
         d*d / 2.0
     }
 }