--- a/src/dassl.cc	Wed Jul 06 14:26:10 1994 +0000
+++ b/src/dassl.cc	Wed Jul 06 14:31:42 1994 +0000
@@ -38,7 +38,7 @@
 #include "f-dassl.h"
 
 // Global pointer for user defined function required by dassl.
-static tree *dassl_fcn;
+static tree_fvc *dassl_fcn;
 
 #ifdef WITH_DLD
 tree_constant *
@@ -94,9 +94,9 @@
       args[2] = deriv;
     }
 
-  if (dassl_fcn != NULL_TREE)
+  if (dassl_fcn != (tree_fvc *) NULL)
     {
-      tree_constant *tmp = dassl_fcn->eval (args, 4, 1, 0);
+      tree_constant *tmp = dassl_fcn->eval (0, 1, args, 4);
 
       delete [] args;
 
@@ -133,7 +133,7 @@
   tree_constant *retval = NULL_TREE_CONST;
 
   dassl_fcn = is_valid_function (args[1], "dassl", 1);
-  if (dassl_fcn == NULL_TREE
+  if (dassl_fcn == (tree_fvc *) NULL
       || takes_correct_nargs (dassl_fcn, 4, "dassl", 1) != 1)
     return retval;
 

--- a/src/fsolve.cc	Wed Jul 06 14:26:10 1994 +0000
+++ b/src/fsolve.cc	Wed Jul 06 14:31:42 1994 +0000
@@ -38,7 +38,7 @@
 #include "f-fsolve.h"
 
 // Global pointer for user defined function required by hybrd1.
-static tree *fsolve_fcn;
+static tree_fvc *fsolve_fcn;
 
 #ifdef WITH_DLD
 tree_constant *
@@ -110,9 +110,9 @@
       args[1] = vars;
     }
 
-  if (fsolve_fcn != NULL_TREE)
+  if (fsolve_fcn != (tree_fvc *) NULL)
     {
-      tree_constant *tmp = fsolve_fcn->eval (args, 2, 1, 0);
+      tree_constant *tmp = fsolve_fcn->eval (0, 1, args, 2);
       delete [] args;
       if (tmp != NULL_TREE_CONST && tmp[0].is_defined ())
 	{
@@ -141,7 +141,7 @@
   tree_constant *retval = NULL_TREE_CONST;
 
   fsolve_fcn = is_valid_function (args[1], "fsolve", 1);
-  if (fsolve_fcn == NULL_TREE
+  if (fsolve_fcn == (tree_fvc *) NULL
       || takes_correct_nargs (fsolve_fcn, 2, "fsolve", 1) != 1)
     return retval;
 

--- a/src/lex.l	Wed Jul 06 14:26:10 1994 +0000
+++ b/src/lex.l	Wed Jul 06 14:31:42 1994 +0000
@@ -52,6 +52,8 @@
 #include "error.h"
 #include "utils.h"
 #include "tree.h"
+#include "tree-plot.h"
+#include "tree-const.h"
 #include "y.tab.h"
 #include "parse.h"
 #include "lex.h"

--- a/src/lsode.cc	Wed Jul 06 14:26:10 1994 +0000
+++ b/src/lsode.cc	Wed Jul 06 14:31:42 1994 +0000
@@ -38,7 +38,7 @@
 #include "f-lsode.h"
 
 // Global pointer for user defined function required by lsode.
-static tree *lsode_fcn;
+static tree_fvc *lsode_fcn;
 
 #ifdef WITH_DLD
 tree_constant *
@@ -83,9 +83,9 @@
       args[1] = state;
     }
 
-  if (lsode_fcn != NULL_TREE)
+  if (lsode_fcn != (tree_fvc *) NULL)
     {
-      tree_constant *tmp = lsode_fcn->eval (args, 3, 1, 0);
+      tree_constant *tmp = lsode_fcn->eval (0, 1, args, 3);
 
       delete [] args;
 
@@ -122,7 +122,7 @@
   tree_constant *retval = NULL_TREE_CONST;
 
   lsode_fcn = is_valid_function (args[1], "lsode", 1);
-  if (lsode_fcn == NULL_TREE
+  if (lsode_fcn == (tree_fvc *) NULL
       || takes_correct_nargs (lsode_fcn, 3, "lsode", 1) != 1)
     return retval;
 

--- a/src/npsol.cc	Wed Jul 06 14:26:10 1994 +0000
+++ b/src/npsol.cc	Wed Jul 06 14:31:42 1994 +0000
@@ -41,8 +41,8 @@
 #include "f-npsol.h"
 
 // Global pointers for user defined functions required by npsol.
-static tree *npsol_objective;
-static tree *npsol_constraints;
+static tree_fvc *npsol_objective;
+static tree_fvc *npsol_constraints;
 
 #ifdef WITH_DLD
 tree_constant *
@@ -88,9 +88,9 @@
   retval = 0.0;
 
   tree_constant objective_value;
-  if (npsol_objective != NULL_TREE)
+  if (npsol_objective != (tree_fvc *) NULL)
     {
-      tree_constant *tmp = npsol_objective->eval (args, 2, 1, 0);
+      tree_constant *tmp = npsol_objective->eval (0, 1, args, 2);
 
       delete [] args;
 
@@ -168,9 +168,9 @@
 //  args[0] = name;
   args[1] = decision_vars;
 
-  if (npsol_constraints != NULL_TREE)
+  if (npsol_constraints != (tree_fvc *)NULL)
     {
-      tree_constant *tmp = npsol_constraints->eval (args, 2, 1, 0);
+      tree_constant *tmp = npsol_constraints->eval (0, 1, args, 2);
 
       delete [] args;
 
@@ -291,7 +291,7 @@
     }
 
   npsol_objective = is_valid_function (args[2], "npsol", 1);
-  if (npsol_objective == NULL_TREE
+  if (npsol_objective == (tree_fvc *) NULL
       || takes_correct_nargs (npsol_objective, 2, "npsol", 1) != 1)
     return retval;
 
@@ -345,13 +345,13 @@
       goto solved;
     }
 
-  npsol_constraints = NULL_TREE;
+  npsol_constraints = (tree_fvc *) NULL;
   if (nargin == 6 || nargin == 8 || nargin == 9 || nargin == 11)
     npsol_constraints = is_valid_function (args[nargin-2], "npsol", 0);
 
   if (nargin == 8 || nargin == 6)
     {
-      if (npsol_constraints == NULL_TREE)
+      if (npsol_constraints == (tree_fvc *) NULL)
 	{
 	  ColumnVector lub = args[nargin-1].to_vector ();
 	  Matrix c = args[nargin-2].to_matrix ();
@@ -424,7 +424,7 @@
 
   if (nargin == 9 || nargin == 11)
     {
-      if (npsol_constraints == NULL_TREE)
+      if (npsol_constraints == (tree_fvc *) NULL)
 	{
 	  // Produce error message.
 	  is_valid_function (args[nargin-2], "npsol", 1);

--- a/src/quad.cc	Wed Jul 06 14:26:10 1994 +0000
+++ b/src/quad.cc	Wed Jul 06 14:31:42 1994 +0000
@@ -39,7 +39,7 @@
 #include "f-quad.h"
 
 // Global pointer for user defined function required by quadrature functions.
-static tree *quad_fcn;
+static tree_fvc *quad_fcn;
 
 #ifdef WITH_DLD
 tree_constant *
@@ -67,9 +67,9 @@
 //  args[0] = name;
   args[1] = tree_constant (x);
 
-  if (quad_fcn != NULL_TREE)
+  if (quad_fcn != (tree_fvc *) NULL)
     {
-      tree_constant *tmp = quad_fcn->eval (args, 2, 1, 0);
+      tree_constant *tmp = quad_fcn->eval (0, 1, args, 2);
 
       delete [] args;
 
@@ -105,7 +105,7 @@
   tree_constant *retval = NULL_TREE_CONST;
 
   quad_fcn = is_valid_function (args[1], "fsolve", 1);
-  if (quad_fcn == NULL_TREE
+  if (quad_fcn == (tree_fvc *) NULL
       || takes_correct_nargs (quad_fcn, 2, "fsolve", 1) != 1)
     return retval;