Add generic Norm object for oops

src/orca-jedi/CMakeLists.txt

@@ -20,6 +20,8 @@ model/ModelBiasCovariance.h
 model/ModelBias.h
 model/ModelBiasIncrement.h
 model/Model.h
+norm/Norm.h
+norm/Norm.cc
 state/State.h
 state/State.cc
 nemo_io/NemoFieldReader.h

src/orca-jedi/norm/Norm.cc

@@ -0,0 +1,37 @@
+/*
+ * (C) British Crown Copyright 2026 Met Office
+ *
+ * This software is licensed under the terms of the Apache Licence Version 2.0
+ * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+ */
+
+#include "orca-jedi/norm/Norm.h"
+
+#include "eckit/exception/Exceptions.h"
+
+namespace orcamodel {
+
+Norm::Norm(const oops::Variables &,
+           const eckit::Configuration &,
+           const State &) {
+  throw eckit::NotImplemented(Here());
+}
+
+void Norm::apply(Increment &) const {
+  throw eckit::NotImplemented(Here());
+}
+
+void Norm::applyInverse(Increment &) const {
+  throw eckit::NotImplemented(Here());
+}
+
+const double Norm::computeNorm(const Increment &) const {
+  throw eckit::NotImplemented(Here());
+  return 0.0;
+}
+
+void Norm::print(std::ostream &) const {
+  throw eckit::NotImplemented(Here());
+}
+
+}  // namespace orcamodel

src/orca-jedi/norm/Norm.h

@@ -0,0 +1,43 @@
+/*
+ * (C) British Crown Copyright 2026 Met Office
+ *
+ * This software is licensed under the terms of the Apache Licence Version 2.0
+ * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "eckit/config/Configuration.h"
+
+#include "oops/base/Variables.h"
+#include "oops/util/ObjectCounter.h"
+#include "oops/util/Printable.h"
+
+#include "orca-jedi/increment/Increment.h"
+#include "orca-jedi/state/State.h"
+
+namespace orcamodel {
+
+class Norm : public util::Printable,
+             private util::ObjectCounter<Norm> {
+ public:
+  static const std::string classname() {return "orcamodel::Norm";}
+
+// Constructor, destructor
+  Norm(const oops::Variables &,
+       const eckit::Configuration &,
+       const State &);
+  ~Norm() = default;
+
+// Apply norm to increment
+  void apply(Increment &) const;
+  void applyInverse(Increment &) const;
+  const double computeNorm(const Increment &) const;
+
+ private:
+  void print(std::ostream &) const override;
+};
+
+}  // namespace orcamodel

src/orca-jedi/utilities/OrcaModelTraits.h

@@ -16,6 +16,7 @@
 #include "orca-jedi/model/ModelBias.h"
 #include "orca-jedi/model/ModelBiasIncrement.h"
 #include "orca-jedi/model/ModelBiasCovariance.h"
+#include "orca-jedi/norm/Norm.h"
 #include "orca-jedi/state/State.h"
 #include "orca-jedi/utilities/ModelData.h"
 #include "orca-jedi/variablechanges/VariableChange.h"
@@ -38,6 +39,7 @@ struct OrcaModelTraits {
   typedef orcamodel::ModelBiasIncrement        ModelAuxIncrement;
   typedef orcamodel::ModelBiasCovariance       ModelAuxCovariance;
   typedef orcamodel::Model                     Model;
+  typedef orcamodel::Norm                      Norm;
   typedef orcamodel::State                     State;
   typedef orcamodel::LinearModel               LinearModel;
   typedef orcamodel::VariableChange            VariableChange;