diff -r 6105b5cd8d89 -r f0e8704d3f0e src/forward_model/bias.rs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/forward_model/bias.rs	Mon Feb 17 13:54:53 2025 -0500
@@ -0,0 +1,108 @@
+/*!
+Simple parametric forward model.
+ */
+
+use super::{AdjointProductBoundedBy, AdjointProductPairBoundedBy, BoundedCurvature, ForwardModel};
+use crate::measures::RNDM;
+use alg_tools::direct_product::Pair;
+use alg_tools::error::DynError;
+use alg_tools::linops::{IdOp, Linear, RowOp, ZeroOp, AXPY};
+use alg_tools::mapping::Space;
+use alg_tools::norms::{Norm, NormExponent, PairNorm, L2};
+use alg_tools::types::{ClosedAdd, Float};
+use numeric_literals::replace_float_literals;
+
+impl<Domain, F, A, E> ForwardModel<Pair<Domain, A::Observable>, F, PairNorm<E, L2, L2>>
+    for RowOp<A, IdOp<A::Observable>>
+where
+    E: NormExponent,
+    Domain: Space + Norm<F, E>,
+    F: Float,
+    A::Observable: ClosedAdd + Norm<F, L2> + 'static,
+    A: ForwardModel<Domain, F, E> + 'static,
+{
+    type Observable = A::Observable;
+
+    fn write_observable(&self, b: &Self::Observable, prefix: String) -> DynError {
+        self.0.write_observable(b, prefix)
+    }
+
+    /// Returns a zero observable
+    fn zero_observable(&self) -> Self::Observable {
+        self.0.zero_observable()
+    }
+}
+
+#[replace_float_literals(F::cast_from(literal))]
+impl<Domain, F, A, D, Z> AdjointProductPairBoundedBy<Pair<Domain, Z>, D, IdOp<Z>>
+    for RowOp<A, IdOp<Z>>
+where
+    Domain: Space,
+    F: Float,
+    Z: Clone + Space + ClosedAdd,
+    A: AdjointProductBoundedBy<Domain, D, FloatType = F, Codomain = Z>,
+    A::Codomain: ClosedAdd,
+{
+    type FloatType = F;
+
+    fn adjoint_product_pair_bound(&self, d: &D, _: &IdOp<Z>) -> Option<(F, F)> {
+        self.0.adjoint_product_bound(d).map(|l_0| {
+            // [A_*; B_*][A, B] = [A_*A, A_* B; B_* A, B_* B] ≤ diag(2A_*A, 2B_*B)
+            // ≤ diag(2l_A𝒟_A, 2l_B𝒟_B), where now 𝒟_B=Id and l_B=1.
+            (2.0 * l_0, 2.0)
+        })
+    }
+}
+
+/*
+/// This `impl` is bit of an abuse as the codomain of `Apre` is a [`Pair`] of a measure predual,
+/// to which this `impl` applies, and another space.
+impl<F, Apre, Z> LipschitzValues
+for ColOp<Apre, IdOp<Z>>
+where
+    F : Float,
+    Z : Clone + Space + ClosedAdd,
+    Apre : LipschitzValues<FloatType = F>,
+{
+    type FloatType = F;
+    /// Return (if one exists) a factor $L$ such that $A_*z$ is $L$-Lipschitz for all
+    /// $z$ in the unit ball.
+    fn value_unit_lipschitz_factor(&self) -> Option<Self::FloatType> {
+        self.0.value_unit_lipschitz_factor()
+    }
+
+    /// Return (if one exists) a factor $L$ such that $∇A_*z$ is $L$-Lipschitz for all
+    /// $z$ in the unit ball.
+    fn value_diff_unit_lipschitz_factor(&self) -> Option<Self::FloatType> {
+        self.0.value_diff_unit_lipschitz_factor()
+    }
+}
+*/
+
+impl<F, A, Z> BoundedCurvature for RowOp<A, IdOp<Z>>
+where
+    F: Float,
+    Z: Clone + Space + ClosedAdd,
+    A: BoundedCurvature<FloatType = F>,
+{
+    type FloatType = F;
+
+    fn curvature_bound_components(&self) -> (Option<Self::FloatType>, Option<Self::FloatType>) {
+        self.0.curvature_bound_components()
+    }
+}
+
+#[replace_float_literals(F::cast_from(literal))]
+impl<'a, F, D, XD, Y, const N: usize> AdjointProductBoundedBy<RNDM<F, N>, D>
+    for ZeroOp<'a, RNDM<F, N>, XD, Y, F>
+where
+    F: Float,
+    Y: AXPY<F> + Clone,
+    D: Linear<RNDM<F, N>>,
+{
+    type FloatType = F;
+    /// Return $L$ such that $A_*A ≤ L𝒟$ is bounded by some `other` operator $𝒟$.
+    fn adjoint_product_bound(&self, _: &D) -> Option<F> {
+        Some(0.0)
+    }
+}