--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/corefcn/inv.cc	Fri Jul 27 15:35:00 2012 -0700
@@ -0,0 +1,250 @@
+/*
+
+Copyright (C) 1996-2012 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 3 of the License, 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, see
+<http://www.gnu.org/licenses/>.
+
+*/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "defun.h"
+#include "error.h"
+#include "gripes.h"
+#include "oct-obj.h"
+#include "ops.h"
+#include "ov-re-diag.h"
+#include "ov-cx-diag.h"
+#include "ov-flt-re-diag.h"
+#include "ov-flt-cx-diag.h"
+#include "ov-perm.h"
+#include "utils.h"
+
+DEFUN (inv, args, nargout,
+  "-*- texinfo -*-\n\
+@deftypefn  {Built-in Function} {@var{x} =} inv (@var{A})\n\
+@deftypefnx {Built-in Function} {[@var{x}, @var{rcond}] =} inv (@var{A})\n\
+Compute the inverse of the square matrix @var{A}.  Return an estimate\n\
+of the reciprocal condition number if requested, otherwise warn of an\n\
+ill-conditioned matrix if the reciprocal condition number is small.\n\
+\n\
+In general it is best to avoid calculating the inverse of a matrix\n\
+directly.  For example, it is both faster and more accurate to solve\n\
+systems of equations (@var{A}*@math{x} = @math{b}) with\n\
+@code{@var{y} = @var{A} \\ @math{b}}, rather than\n\
+@code{@var{y} = inv (@var{A}) * @math{b}}.\n\
+\n\
+If called with a sparse matrix, then in general @var{x} will be a full\n\
+matrix requiring significantly more storage.  Avoid forming the inverse\n\
+of a sparse matrix if possible.\n\
+@seealso{ldivide, rdivide}\n\
+@end deftypefn")
+{
+  octave_value_list retval;
+
+  int nargin = args.length ();
+
+  if (nargin != 1)
+    {
+      print_usage ();
+      return retval;
+    }
+
+  octave_value arg = args(0);
+
+  octave_idx_type nr = arg.rows ();
+  octave_idx_type nc = arg.columns ();
+
+  int arg_is_empty = empty_arg ("inverse", nr, nc);
+
+  if (arg_is_empty < 0)
+    return retval;
+  else if (arg_is_empty > 0)
+    return octave_value (Matrix ());
+
+  if (nr != nc)
+    {
+      gripe_square_matrix_required ("inverse");
+      return retval;
+    }
+
+  octave_value result;
+  octave_idx_type info;
+  double rcond = 0.0;
+  float frcond = 0.0;
+  bool isfloat = arg.is_single_type ();
+
+  if (arg.is_diag_matrix ())
+    {
+      rcond = 1.0;
+      frcond = 1.0f;
+      if (arg.is_complex_type ())
+        {
+          if (isfloat)
+            {
+              result = arg.float_complex_diag_matrix_value ().inverse (info);
+              if (nargout > 1)
+                frcond = arg.float_complex_diag_matrix_value ().rcond ();
+            }
+          else
+            {
+              result = arg.complex_diag_matrix_value ().inverse (info);
+              if (nargout > 1)
+                rcond = arg.complex_diag_matrix_value ().rcond ();
+            }
+        }
+      else
+        {
+          if (isfloat)
+            {
+              result = arg.float_diag_matrix_value ().inverse (info);
+              if (nargout > 1)
+                frcond = arg.float_diag_matrix_value ().rcond ();
+            }
+          else
+            {
+              result = arg.diag_matrix_value ().inverse (info);
+              if (nargout > 1)
+                rcond = arg.diag_matrix_value ().rcond ();
+            }
+        }
+    }
+  else if (arg.is_perm_matrix ())
+    {
+      rcond = 1.0;
+      info = 0;
+      result = arg.perm_matrix_value ().inverse ();
+    }
+  else if (isfloat)
+    {
+      if (arg.is_real_type ())
+        {
+          FloatMatrix m = arg.float_matrix_value ();
+          if (! error_state)
+            {
+              MatrixType mattyp = args(0).matrix_type ();
+              result = m.inverse (mattyp, info, frcond, 1);
+              args(0).matrix_type (mattyp);
+            }
+        }
+      else if (arg.is_complex_type ())
+        {
+          FloatComplexMatrix m = arg.float_complex_matrix_value ();
+          if (! error_state)
+            {
+              MatrixType mattyp = args(0).matrix_type ();
+              result = m.inverse (mattyp, info, frcond, 1);
+              args(0).matrix_type (mattyp);
+            }
+        }
+    }
+  else
+    {
+      if (arg.is_real_type ())
+        {
+          if (arg.is_sparse_type ())
+            {
+              SparseMatrix m = arg.sparse_matrix_value ();
+              if (! error_state)
+                {
+                  MatrixType mattyp = args(0).matrix_type ();
+                  result = m.inverse (mattyp, info, rcond, 1);
+                  args(0).matrix_type (mattyp);
+                }
+            }
+          else
+            {
+              Matrix m = arg.matrix_value ();
+              if (! error_state)
+                {
+                  MatrixType mattyp = args(0).matrix_type ();
+                  result = m.inverse (mattyp, info, rcond, 1);
+                  args(0).matrix_type (mattyp);
+                }
+            }
+        }
+      else if (arg.is_complex_type ())
+        {
+          if (arg.is_sparse_type ())
+            {
+              SparseComplexMatrix m = arg.sparse_complex_matrix_value ();
+              if (! error_state)
+                {
+                  MatrixType mattyp = args(0).matrix_type ();
+                  result = m.inverse (mattyp, info, rcond, 1);
+                  args(0).matrix_type (mattyp);
+                }
+            }
+          else
+            {
+              ComplexMatrix m = arg.complex_matrix_value ();
+              if (! error_state)
+                {
+                  MatrixType mattyp = args(0).matrix_type ();
+                  result = m.inverse (mattyp, info, rcond, 1);
+                  args(0).matrix_type (mattyp);
+                }
+            }
+        }
+      else
+        gripe_wrong_type_arg ("inv", arg);
+    }
+
+  if (! error_state)
+    {
+      if (nargout > 1)
+        retval(1) = isfloat ? octave_value (frcond) : octave_value (rcond);
+
+      retval(0) = result;
+
+      volatile double xrcond = rcond;
+      xrcond += 1.0;
+      if (nargout < 2 && (info == -1 || xrcond == 1.0))
+        warning ("inverse: matrix singular to machine precision, rcond = %g",
+                 rcond);
+    }
+
+  return retval;
+}
+
+/*
+%!assert (inv ([1, 2; 3, 4]), [-2, 1; 1.5, -0.5], sqrt (eps))
+%!assert (inv (single ([1, 2; 3, 4])), single ([-2, 1; 1.5, -0.5]), sqrt (eps ("single")))
+
+%!error inv ()
+%!error inv ([1, 2; 3, 4], 2)
+%!error <argument must be a square matrix> inv ([1, 2; 3, 4; 5, 6])
+*/
+
+// FIXME -- this should really be done with an alias, but
+// alias_builtin() won't do the right thing if we are actually using
+// dynamic linking.
+
+DEFUN (inverse, args, nargout,
+  "-*- texinfo -*-\n\
+@deftypefn  {Built-in Function} {@var{x} =} inverse (@var{A})\n\
+@deftypefnx {Built-in Function} {[@var{x}, @var{rcond}] =} inverse (@var{A})\n\
+Compute the inverse of the square matrix @var{A}.\n\
+\n\
+This is an alias for @code{inv}.\n\
+@seealso{inv}\n\
+@end deftypefn")
+{
+  return Finv (args, nargout);
+}