rework substitution of diff nodes using new node comparison methods

src/DynamicModel.cc

@@ -5399,7 +5399,7 @@ DynamicModel::substituteUnaryOps(vector<int> &eqnumbers)
 }
 
 void
-DynamicModel::substituteDiff(StaticModel &static_model, ExprNode::subst_table_t &diff_subst_table)
+DynamicModel::substituteDiff(ExprNode::subst_table_t &diff_subst_table)
 {
   set<int> used_local_vars;
   for (const auto & equation : equations)
@@ -5409,21 +5409,21 @@ DynamicModel::substituteDiff(StaticModel &static_model, ExprNode::subst_table_t
   diff_table_t diff_table;
   for (auto & it : local_variables_table)
     if (used_local_vars.find(it.first) != used_local_vars.end())
-      it.second->findDiffNodes(static_model, diff_table);
+      it.second->findDiffNodes(diff_table);
 
   for (const auto & equation : equations)
-    equation->findDiffNodes(static_model, diff_table);
+    equation->findDiffNodes(diff_table);
 
   // Substitute in model local variables
   vector<BinaryOpNode *> neweqs;
   for (auto & it : local_variables_table)
-    it.second = it.second->substituteDiff(static_model, diff_table, diff_subst_table, neweqs);
+    it.second = it.second->substituteDiff(diff_table, diff_subst_table, neweqs);
 
   // Substitute in equations
   for (auto & equation : equations)
     {
       auto *substeq = dynamic_cast<BinaryOpNode *>(equation->
-                                                   substituteDiff(static_model, diff_table, diff_subst_table, neweqs));
+                                                   substituteDiff(diff_table, diff_subst_table, neweqs));
       assert(substeq != nullptr);
       equation = substeq;
     }

src/DynamicModel.hh

@@ -432,7 +432,7 @@ public:
   void substituteUnaryOps(vector<int> &eqnumbers);
 
   //! Substitutes diff operator
-  void substituteDiff(StaticModel &static_model, ExprNode::subst_table_t &diff_subst_table);
+  void substituteDiff(ExprNode::subst_table_t &diff_subst_table);
 
   //! Table to undiff LHS variables for pac vector z
   void getUndiffLHSForPac(vector<int> &lhs, vector<expr_t> &lhs_expr_t, vector<bool> &diff, vector<int> &orig_diff_var,

src/ModFile.cc

@@ -372,7 +372,7 @@ ModFile::transformPass(bool nostrict, bool stochastic, bool compute_xrefs, const
 
   // Create auxiliary variable and equations for Diff operators that appear in VAR equations
   ExprNode::subst_table_t diff_subst_table;
-  dynamic_model.substituteDiff(diff_static_model, diff_subst_table);
+  dynamic_model.substituteDiff(diff_subst_table);
 
   // Var Model
   map<string, vector<string>> var_model_eq_tags;

src/SymbolTable.cc

@@ -715,12 +715,14 @@ SymbolTable::addExpectationAuxiliaryVar(int information_set, int index, expr_t e
 }
 
 int
-SymbolTable::addDiffLagAuxiliaryVar(int index, expr_t expr_arg, int orig_symb_id, int orig_lag) noexcept(false)
+SymbolTable::addDiffLagAuxiliaryVar(int index, expr_t expr_arg,
+                                    int lag,
+                                    int orig_symb_id, int orig_lag) noexcept(false)
 {
   ostringstream varname;
   int symb_id;
 
-  varname << "AUX_DIFF_LAG_" << index;
+  varname << "AUX_DIFF_" << index << "_LAG_" << lag;
 
   try
     {

src/SymbolTable.hh

@@ -293,7 +293,7 @@ public:
   int addDiffAuxiliaryVar(int index, expr_t expr_arg) noexcept(false);
   int addDiffAuxiliaryVar(int index, expr_t expr_arg, int orig_symb_id, int orig_lag) noexcept(false);
   //! Takes care of timing between diff statements
-  int addDiffLagAuxiliaryVar(int index, expr_t expr_arg, int orig_symb_id, int orig_lag) noexcept(false);
+  int addDiffLagAuxiliaryVar(int index, expr_t expr_arg, int lag, int orig_symb_id, int orig_lag) noexcept(false);
   //! An Auxiliary variable for a unary op
   int addUnaryOpAuxiliaryVar(int index, expr_t expr_arg, int orig_symb_id = -1, int orig_lag = 0) noexcept(false);
   //! Returns the number of auxiliary variables