Added old code back wrapped in deprecated flag

gtsam/linear/NoiseModel.cpp

@@ -826,6 +826,24 @@ Welsch::shared_ptr Welsch::Create(double c, const ReweightScheme reweight) {
   return shared_ptr(new Welsch(c, reweight));
 }
 
+#ifdef GTSAM_ALLOW_DEPRECATED_SINCE_V4
+Welsh::Welsh(double c, const ReweightScheme reweight) : Base(reweight), c_(c), csquared_(c * c) {}
+
+void Welsh::print(const std::string &s="") const {
+  std::cout << s << ": Welsh (" << c_ << ")" << std::endl;
+}
+
+bool Welsh::equals(const Base &expected, double tol) const {
+  const Welsh* p = dynamic_cast<const Welsh*>(&expected);
+  if (p == NULL) return false;
+  return std::abs(c_ - p->c_) < tol;
+}
+
+Welsh::shared_ptr Welsh::Create(double c, const ReweightScheme reweight) {
+  return shared_ptr(new Welsh(c, reweight));
+}
+#endif
+
 /* ************************************************************************* */
 // GemanMcClure
 /* ************************************************************************* */

gtsam/linear/NoiseModel.h

@@ -878,6 +878,38 @@ namespace gtsam {
           ar & BOOST_SERIALIZATION_NVP(c_);
         }
       };
+#ifdef GTSAM_ALLOW_DEPRECATED_SINCE_V4
+      /// @name Deprecated
+      /// @{
+      // Welsh implements the "Welsch" robust error model (Zhang97ivc)
+      // This was misspelled in previous versions of gtsam and should be
+      // removed in the future.
+      class GTSAM_EXPORT Welsh : public Base {
+      protected:
+        double c_, csquared_;
+
+      public:
+        typedef boost::shared_ptr<Welsh> shared_ptr;
+
+        Welsh(double c = 2.9846, const ReweightScheme reweight = Block);
+        double weight(double error) const {
+          double xc2 = (error*error)/csquared_;
+          return std::exp(-xc2);
+        }
+        void print(const std::string &s) const;
+        bool equals(const Base& expected, double tol=1e-8) const;
+        static shared_ptr Create(double k, const ReweightScheme reweight = Block) ;
+
+      private:
+        /** Serialization function */
+        friend class boost::serialization::access;
+        template<class ARCHIVE>
+        void serialize(ARCHIVE & ar, const unsigned int /*version*/) {
+          ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
+          ar & BOOST_SERIALIZATION_NVP(c_);
+        }
+      };
+#endif
 
       /// GemanMcClure implements the "Geman-McClure" robust error model
       /// (Zhang97ivc).