new file mode 100644
--- /dev/null
+++ b/src/pt-check.cc
@@ -0,0 +1,637 @@
+/*
+
+Copyright (C) 1996, 1997 John W. Eaton
+
+This file is part of Octave.
+
+Octave is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option) any
+later version.
+
+Octave is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with Octave; see the file COPYING.  If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+
+*/
+
+#if defined (__GNUG__)
+#pragma implementation
+#endif
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "error.h"
+#include "input.h"
+#include "ov-usr-fcn.h"
+#include "pt-all.h"
+
+void
+tree_checker::visit_argument_list (tree_argument_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_expression *elt = lst (p);
+
+      lst.next (p);
+
+      if (elt)
+	{
+	  if (do_lvalue_check && ! elt->lvalue_ok ())
+	    gripe ("invalid lvalue in multiple assignment", elt->line ());
+	}
+    }
+}
+
+void
+tree_checker::visit_binary_expression (tree_binary_expression& expr)
+{
+  tree_expression *op1 = expr.lhs ();
+
+  if (op1)
+    op1->accept (*this);
+
+  tree_expression *op2 = expr.rhs ();
+
+  if (op2)
+    op2->accept (*this);
+}
+
+void
+tree_checker::visit_break_command (tree_break_command&)
+{
+}
+
+void
+tree_checker::visit_colon_expression (tree_colon_expression& expr)
+{
+  tree_expression *op1 = expr.base ();
+
+  if (op1)
+    op1->accept (*this);
+
+  tree_expression *op3 = expr.increment ();
+
+  if (op3)
+    op3->accept (*this);
+
+  tree_expression *op2 = expr.limit ();
+
+  if (op2)
+    op2->accept (*this);
+}
+
+void
+tree_checker::visit_continue_command (tree_continue_command&)
+{
+}
+
+void
+tree_checker::visit_decl_command (tree_decl_command& cmd)
+{
+  tree_decl_init_list *init_list = cmd.initializer_list ();
+
+  if (init_list)
+    init_list->accept (*this);
+}
+
+void
+tree_checker::visit_decl_elt (tree_decl_elt& cmd)
+{
+  tree_identifier *id = cmd.ident ();
+
+  if (id)
+    id->accept (*this);
+
+  tree_expression *expr = cmd.expression ();
+
+  if (expr)
+    expr->accept (*this);
+}
+
+void
+tree_checker::visit_decl_init_list (tree_decl_init_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_decl_elt *elt = lst (p);
+
+      lst.next (p);
+
+      if (elt)
+	elt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_simple_for_command (tree_simple_for_command& cmd)
+{
+  tree_expression *lhs = cmd.left_hand_side ();
+
+  if (lhs)
+    {
+      if (! lhs->lvalue_ok ())
+	gripe ("invalid lvalue in for command", cmd.line ());
+    }
+
+  tree_expression *expr = cmd.control_expr ();
+
+  if (expr)
+    expr->accept (*this);
+
+  tree_statement_list *list = cmd.body ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_complex_for_command (tree_complex_for_command& cmd)
+{
+  tree_argument_list *lhs = cmd.left_hand_side ();
+
+  if (lhs)
+    {
+      int len = lhs->length ();
+
+      if (len == 0 || lhs > 2)
+	gripe ("invalid number of output arguments in for command",
+	       cmd.line ());
+
+      do_lvalue_check = true;
+
+      lhs->accept (*this);
+
+      do_lvalue_check = false;
+    }
+
+  tree_expression *expr = cmd.control_expr ();
+
+  if (expr)
+    expr->accept (*this);
+
+  tree_statement_list *list = cmd.body ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_octave_user_function (octave_user_function& fcn)
+{
+  tree_statement_list *cmd_list = fcn.body ();
+
+  if (cmd_list)
+    cmd_list->accept (*this);
+}
+
+void
+tree_checker::visit_identifier (tree_identifier& /* id */)
+{
+}
+
+void
+tree_checker::visit_if_clause (tree_if_clause& cmd)
+{
+  tree_expression *expr = cmd.condition ();
+
+  if (expr)
+    expr->accept (*this);
+
+  tree_statement_list *list = cmd.commands ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_if_command (tree_if_command& cmd)
+{
+  tree_if_command_list *list = cmd.cmd_list ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_if_command_list (tree_if_command_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_if_clause *elt = lst (p);
+
+      if (elt)
+	elt->accept (*this);
+
+      lst.next (p);
+    }
+}
+
+void
+tree_checker::visit_index_expression (tree_index_expression& expr)
+{
+  tree_expression *e = expr.expression ();
+
+  if (e)
+    e->accept (*this);
+
+  tree_argument_list *list = expr.arg_list ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_indirect_ref (tree_indirect_ref& expr)
+{
+  tree_expression *e = expr.expression ();
+
+  if (e)
+    e->accept (*this);
+}
+
+void
+tree_checker::visit_matrix (tree_matrix& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_argument_list *elt = lst (p);
+
+      lst.next (p);
+
+      if (elt)
+	elt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_multi_assignment (tree_multi_assignment& expr)
+{
+  tree_argument_list *lhs = expr.left_hand_side ();
+
+  if (lhs)
+    {
+      do_lvalue_check = true;
+
+      lhs->accept (*this);
+
+      do_lvalue_check = false;
+    }
+
+  tree_expression *rhs = expr.right_hand_side ();
+
+  if (rhs)
+    rhs->accept (*this);
+}
+
+void
+tree_checker::visit_no_op_command (tree_no_op_command& /* cmd */)
+{
+}
+
+void
+tree_checker::visit_constant (tree_constant& /* val */)
+{
+}
+
+void
+tree_checker::visit_parameter_list (tree_parameter_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_identifier *elt = lst (p);
+
+      lst.next (p);
+
+      if (elt)
+	elt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_plot_command (tree_plot_command& cmd)
+{
+  plot_limits *range = cmd.limits ();
+
+  if (range)
+    range->accept (*this);
+
+  subplot_list *plot_list = cmd.subplots ();
+
+  if (plot_list)
+    plot_list->accept (*this);
+}
+
+void
+tree_checker::visit_plot_limits (plot_limits& cmd)
+{
+  plot_range *x_range = cmd.x_limits ();
+
+  if (x_range)
+    x_range->accept (*this);
+
+  plot_range *y_range = cmd.y_limits ();
+
+  if (y_range)
+    y_range->accept (*this);
+
+  plot_range *z_range = cmd.z_limits ();
+
+  if (z_range)
+    z_range->accept (*this);
+}
+
+void
+tree_checker::visit_plot_range (plot_range& cmd)
+{
+  tree_expression *lower = cmd.lower_bound ();
+
+  if (lower)
+    lower->accept (*this);
+
+  tree_expression *upper = cmd.upper_bound ();
+
+  if (upper)
+    upper->accept (*this);
+}
+
+void
+tree_checker::visit_postfix_expression (tree_postfix_expression& expr)
+{
+  tree_expression *e = expr.operand ();
+
+  if (e)
+    e->accept (*this);
+}
+
+void
+tree_checker::visit_prefix_expression (tree_prefix_expression& expr)
+{
+  tree_expression *e = expr.operand ();
+
+  if (e)
+    e->accept (*this);
+}
+
+void
+tree_checker::visit_return_command (tree_return_command&)
+{
+}
+
+void
+tree_checker::visit_return_list (tree_return_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_index_expression *elt = lst (p);
+
+      lst.next (p);
+
+      if (elt)
+	elt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_simple_assignment (tree_simple_assignment& expr)
+{
+  tree_expression *lhs = expr.left_hand_side ();
+
+  if (lhs)
+    {
+      if (! lhs->lvalue_ok ())
+	gripe ("invalid lvalue in assignment", expr.line ());
+    }
+
+  tree_expression *rhs = expr.right_hand_side ();
+
+  if (rhs)
+    rhs->accept (*this);
+}
+
+void
+tree_checker::visit_statement (tree_statement& stmt)
+{
+  tree_command *cmd = stmt.command ();
+
+  if (cmd)
+    cmd->accept (*this);
+  else
+    {
+      tree_expression *expr = stmt.expression ();
+
+      if (expr)
+	expr->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_statement_list (tree_statement_list& lst)
+{
+  for (Pix p = lst.first (); p != 0; lst.next (p))
+    {
+      tree_statement *elt = lst (p);
+
+      if (elt)
+	elt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_subplot (subplot& cmd)
+{
+  tree_expression *sp_plot_data = cmd.plot_data ();
+
+  if (sp_plot_data)
+    sp_plot_data->accept (*this);
+
+  subplot_using *sp_using_clause = cmd.using_clause ();
+
+  if (sp_using_clause)
+    sp_using_clause->accept (*this);
+
+  tree_expression *sp_title_clause = cmd.title_clause ();
+
+  if (sp_title_clause)
+    sp_title_clause->accept (*this);
+
+  subplot_style *sp_style_clause = cmd.style_clause ();
+
+  if (sp_style_clause)
+    sp_style_clause->accept (*this);
+}
+
+void
+tree_checker::visit_subplot_list (subplot_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      subplot *elt = lst (p);
+
+      lst.next (p);
+
+      if (elt)
+	elt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_subplot_style (subplot_style& cmd)
+{
+  tree_expression *sp_linetype = cmd.linetype ();
+
+  if (sp_linetype)
+    sp_linetype->accept (*this);
+
+  tree_expression *sp_pointtype = cmd.pointtype ();
+
+  if (sp_pointtype)
+    sp_pointtype->accept (*this);
+}
+
+void
+tree_checker::visit_subplot_using (subplot_using& cmd)
+{
+  int qual_count = cmd.qualifier_count ();
+
+  if (qual_count > 0)
+    {
+      tree_expression **x = cmd.qualifiers ();
+
+      for (int i = 0; i < qual_count; i++)
+	{
+	  if (x[i])
+	    x[i]->accept (*this);
+	}
+    }
+  else
+    {
+      tree_expression *scanf_fmt = cmd.scanf_format ();
+
+      if (scanf_fmt)
+	scanf_fmt->accept (*this);
+    }
+}
+
+void
+tree_checker::visit_switch_case (tree_switch_case& cs)
+{
+  tree_expression *label = cs.case_label ();
+
+  if (label)
+    label->accept (*this);
+
+  tree_statement_list *list = cs.commands ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_switch_case_list (tree_switch_case_list& lst)
+{
+  Pix p = lst.first ();
+
+  while (p)
+    {
+      tree_switch_case *elt = lst (p);
+
+      if (elt)
+	elt->accept (*this);
+
+      lst.next (p);
+    }
+}
+
+void
+tree_checker::visit_switch_command (tree_switch_command& cmd)
+{
+  tree_expression *expr = cmd.switch_value ();
+
+  if (expr)
+    expr->accept (*this);
+
+  tree_switch_case_list *list = cmd.case_list ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::visit_try_catch_command (tree_try_catch_command& cmd)
+{
+  tree_statement_list *try_code = cmd.body ();
+
+  if (try_code)
+    try_code->accept (*this);
+
+  tree_statement_list *catch_code = cmd.cleanup ();
+
+  if (catch_code)
+    catch_code->accept (*this);
+}
+
+void
+tree_checker::visit_unwind_protect_command
+  (tree_unwind_protect_command& cmd)
+{
+  tree_statement_list *unwind_protect_code = cmd.body ();
+
+  if (unwind_protect_code)
+    unwind_protect_code->accept (*this);
+
+  tree_statement_list *cleanup_code = cmd.cleanup ();
+
+  if (cleanup_code)
+    cleanup_code->accept (*this);
+}
+
+void
+tree_checker::visit_while_command (tree_while_command& cmd)
+{
+  tree_expression *expr = cmd.condition ();
+
+  if (expr)
+    expr->accept (*this);
+
+  tree_statement_list *list = cmd.body ();
+
+  if (list)
+    list->accept (*this);
+}
+
+void
+tree_checker::gripe (const string& msg, int line)
+{
+  if (curr_fcn_file_name.empty ())
+    error ("%s", msg.c_str ());
+  else
+    error ("%s: %d: %s", curr_fcn_file_name.c_str (), line, msg.c_str ());
+}
+
+/*
+;;; Local Variables: ***
+;;; mode: C++ ***
+;;; End: ***
+*/