diff -r c5f70e767511 -r f802ddbabcfc src/convex.rs
--- a/src/convex.rs	Tue Dec 31 08:48:50 2024 -0500
+++ b/src/convex.rs	Mon Dec 23 23:27:45 2024 -0500
@@ -4,9 +4,9 @@
 
 use std::marker::PhantomData;
 use crate::types::*;
-use crate::mapping::{Mapping, Space};
+use crate::mapping::{Mapping, Space, ArithmeticTrue};
 use crate::linops::IdOp;
-use crate::instance::{Instance, InstanceMut, DecompositionMut};
+use crate::instance::{Instance, InstanceMut, DecompositionMut,};
 use crate::norms::*;
 
 /// Trait for convex mappings. Has no features, just serves as a constraint
@@ -85,6 +85,7 @@
     E : NormExponent,
 {
     type Codomain = F;
+    type ArithmeticOptIn = ArithmeticTrue;
 
     fn apply<I : Instance<Domain>>(&self, d : I) -> F {
         if d.eval(|x| x.norm(self.0.exponent)) <= F::ONE {
@@ -118,6 +119,53 @@
     }
 }
 
+impl<Domain, E, F> Prox<Domain> for NormConjugate<F, E>
+where
+    Domain : Space + Norm<F, E>,
+    E : NormExponent,
+    F : Float,
+    NormProjection<F, E> : Mapping<Domain, Codomain=Domain>,
+{
+    type Prox<'a> = NormProjection<F, E> where Self : 'a;
+
+    #[inline]
+    fn prox_mapping(&self, τ : Self::Codomain) -> Self::Prox<'_> {
+        NormProjection{ α : τ, exponent : self.0.exponent }
+    }
+}
+
+pub struct NormProjection<F : Float, E : NormExponent> {
+    α : F,
+    exponent : E,
+}
+
+/*
+impl<F, Domain> Mapping<Domain> for NormProjection<F, L2>
+where
+    Domain : Space + Euclidean<F> + std::ops::MulAssign<F>,
+    F : Float,
+{
+    type Codomain = Domain;
+
+    fn apply<I : Instance<Domain>>(&self, d : I) -> Domain {
+        d.own().proj_ball2(self.α)
+    }
+}
+*/
+
+impl<F, E, Domain> Mapping<Domain> for NormProjection<F, E>
+where
+    Domain : Space + Projection<F, E> + std::ops::MulAssign<F>,
+    F : Float,
+    E : NormExponent,
+{
+    type Codomain = Domain;
+    type ArithmeticOptIn = ArithmeticTrue;
+
+    fn apply<I : Instance<Domain>>(&self, d : I) -> Domain {
+        d.own().proj_ball(self.α, self.exponent)
+    }
+}
 
 /// The zero mapping
 pub struct Zero<Domain : Space, F : Num>(PhantomData<(Domain, F)>);
@@ -130,6 +178,7 @@
 
 impl<Domain : Space, F : Num> Mapping<Domain> for Zero<Domain, F> {
     type Codomain = F;
+    type ArithmeticOptIn = ArithmeticTrue;
 
     /// Compute the value of `self` at `x`.
     fn apply<I : Instance<Domain>>(&self, _x : I) -> Self::Codomain {
@@ -183,6 +232,7 @@
 
 impl<Domain : Normed<F>, F : Float> Mapping<Domain> for ZeroIndicator<Domain, F> {
     type Codomain = F;
+    type ArithmeticOptIn = ArithmeticTrue;
 
     /// Compute the value of `self` at `x`.
     fn apply<I : Instance<Domain>>(&self, x : I) -> Self::Codomain {