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+++ b/liboctave/DiagArray2.h
@@ -0,0 +1,250 @@
+// Template array classes                              -*- C++ -*-
+/*
+
+Copyright (C) 1996 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 (octave_DiagArray2_h)
+#define octave_DiagArray2_h 1
+
+#if defined (__GNUG__)
+#pragma interface
+#endif
+
+#define HEAVYWEIGHT_INDEXING 1
+
+#include <cassert>
+#include <cstdlib>
+
+#include "Array2.h"
+#include "lo-error.h"
+
+class idx_vector;
+
+// A two-dimensional array with diagonal elements only.
+//
+// Idea and example code for Proxy class and functions from:
+//
+// From: kanze@us-es.sel.de (James Kanze)
+// Subject: Re: How to overload [] to do READ/WRITE differently ?
+// Message-ID: <KANZE.93Nov29151407@slsvhdt.us-es.sel.de>
+// Sender: news@us-es.sel.de
+// Date: 29 Nov 1993 14:14:07 GMT
+// --
+// James Kanze                             email: kanze@us-es.sel.de
+// GABI Software, Sarl., 8 rue du Faisan, F-67000 Strasbourg, France
+
+template <class T>
+class DiagArray2 : public Array<T>
+{
+private:
+
+  T get (int i) { return Array<T>::xelem (i); }
+
+  void set (const T& val, int i) { Array<T>::xelem (i) = val; }
+
+  class Proxy
+  {
+  public:
+
+    Proxy (DiagArray2<T> *ref, int r, int c)
+      : i (r), j (c), object (ref) { } 
+
+    const Proxy& operator = (const T& val) const
+      {
+	if (i == j)
+	  {
+	    if (object)
+	      object->set (val, i);
+	  }
+	else
+	  (*current_liboctave_error_handler)
+	    ("invalid assignment to off-diagonal in diagonal array");
+
+	return *this;
+      }
+
+    operator T () const
+      {
+	if (object && i == j)
+	  return object->get (i);
+	else
+	  {
+	    static T foo (0);
+	    return foo;
+	  }
+      }
+
+  private:
+
+    // XXX FIXME XXX -- this is declared private to keep the user from
+    // taking the address of a Proxy.  Maybe it should be implemented
+    // by means of a companion function in the DiagArray2 class.
+
+    T *operator& () const { assert (0); return (T *) 0; }
+
+    int i;
+    int j;
+
+    DiagArray2<T> *object;
+
+  };
+
+friend class Proxy;
+
+protected:
+
+  int nr;
+  int nc;
+
+  DiagArray2 (T *d, int r, int c) : Array<T> (d, r < c ? r : c)
+    {
+      nr = r;
+      nc = c;
+      set_max_indices (2);
+    }
+
+public:
+
+  DiagArray2 (void) : Array<T> ()
+    {
+      nr = 0;
+      nc = 0;
+      set_max_indices (2);
+    }
+
+  DiagArray2 (int r, int c) : Array<T> (r < c ? r : c)
+    {
+      nr = r;
+      nc = c;
+      set_max_indices (2);
+    }
+
+  DiagArray2 (int r, int c, const T& val) : Array<T> (r < c ? r : c, val)
+    {
+      nr = r;
+      nc = c;
+      set_max_indices (2);
+    }
+
+  DiagArray2 (const Array<T>& a) : Array<T> (a)
+    {
+      nr = nc = a.length ();
+      set_max_indices (2);
+    }
+
+  DiagArray2 (const DiagArray2<T>& a) : Array<T> (a)
+    {
+      nr = a.nr;
+      nc = a.nc;
+      set_max_indices (2);
+    }
+
+  ~DiagArray2 (void) { }
+
+  DiagArray2<T>& operator = (const DiagArray2<T>& a)
+    {
+      if (this != &a)
+	{
+	  Array<T>::operator = (a);
+	  nr = a.nr;
+	  nc = a.nc;
+	}
+
+      return *this;
+    }
+
+#if 0
+  operator Array2<T> () const
+    {
+      Array2<T> retval (nr, nc,  T (0));
+
+      int len = nr < nc ? nr : nc;
+
+      for (int i = 0; i < len; i++)
+	retval.xelem (i, i) = xelem (i, i);
+
+      return retval;
+    }
+#endif
+
+  int dim1 (void) const { return nr; }
+  int dim2 (void) const { return nc; }
+
+  int rows (void) const { return nr; }
+  int cols (void) const { return nc; }
+  int columns (void) const { return nc; }
+
+#if 1
+  Proxy elem (int r, int c)
+    {
+      return Proxy (this, r, c);
+    }
+
+  Proxy checkelem (int r, int c)
+    {
+      if (r < 0 || c < 0 || r >= nr || c >= nc)
+	{
+	  (*current_liboctave_error_handler) ("range error");
+	  return Proxy (0, r, c);
+	}
+      else
+	return Proxy (this, r, c);
+    }
+
+  Proxy operator () (int r, int c)
+    {
+      if (r < 0 || c < 0 || r >= nr || c >= nc)
+	{
+	  (*current_liboctave_error_handler) ("range error");
+	  return Proxy (0, r, c);
+	}
+      else
+	return Proxy (this, r, c);
+  }
+#else
+  T& elem (int r, int c);
+  T& checkelem (int r, int c);
+  T& operator () (int r, int c);
+#endif
+
+  T elem (int r, int c) const;
+  T checkelem (int r, int c) const;
+  T operator () (int r, int c) const;
+
+  // No checking.
+
+  T& xelem (int r, int c);
+  T xelem (int r, int c) const;
+
+  void resize (int n, int m);
+  void resize (int n, int m, const T& val);
+
+  void maybe_delete_elements (idx_vector& i, idx_vector& j);
+};
+
+#endif
+
+/*
+;;; Local Variables: ***
+;;; mode: C++ ***
+;;; page-delimiter: "^/\\*" ***
+;;; End: ***
+*/