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+/*
+
+Copyright (C) 2008 Jaroslav Hajek
+
+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/>.
+
+*/
+
+#if !defined (octave_PermMatrix_h)
+#define octave_PermMatrix_h 1
+
+#include "Array.h"
+#include "mx-defs.h"
+
+class PermMatrix : public Array<octave_idx_type>
+{
+private:
+
+  octave_idx_type get (octave_idx_type i) const { return Array<octave_idx_type>::xelem (i); }
+
+public:
+
+  PermMatrix (void) : Array<octave_idx_type> (), _colp (false) { }
+
+  PermMatrix (octave_idx_type n);
+
+  PermMatrix (const Array<octave_idx_type>& p, bool colp = false, 
+              bool check = true);
+
+  PermMatrix (const PermMatrix& m)
+    : Array<octave_idx_type> (m), _colp(m._colp) 
+    { this->dimensions = m.dims (); }
+  
+  PermMatrix (const idx_vector& idx, bool colp = false, octave_idx_type n = 0); 
+
+  octave_idx_type 
+  elem (octave_idx_type i, octave_idx_type j) const
+    {
+      return (_colp 
+              ? ((get(j) != i) ? 1 : 0)
+              : ((get(i) != j) ? 1 : 0));
+    }
+
+  octave_idx_type 
+  checkelem (octave_idx_type i, octave_idx_type j) const;
+
+  octave_idx_type
+  operator () (octave_idx_type i, octave_idx_type j) const
+    {
+#if defined (BOUNDS_CHECKING)
+      return checkelem (i, j);
+#else
+      return elem (i, j);
+#endif
+    }
+  
+  // These are, in fact, super-fast.
+  PermMatrix transpose (void) const;
+  PermMatrix inverse (void) const;
+
+  // Determinant, i.e. the sign of permutation.
+  octave_idx_type determinant (void) const;
+
+  bool is_col_perm (void) const { return _colp; }
+  bool is_row_perm (void) const { return !_colp; }
+
+  friend PermMatrix operator *(const PermMatrix& a, const PermMatrix& b);
+
+private:
+  bool _colp;
+};
+
+// Multiplying permutations together.
+PermMatrix 
+operator *(const PermMatrix& a, const PermMatrix& b);
+
+#endif