// Template sparse array class
/*

Copyright (C) 2004-2012 David Bateman
Copyright (C) 1998-2004 Andy Adler
Copyright (C) 2010 VZLU Prague

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 <cassert>
#include <climits>

#include <algorithm>
#include <iostream>
#include <sstream>
#include <vector>

#include "Array.h"
#include "MArray.h"
#include "Array-util.h"
#include "Range.h"
#include "idx-vector.h"
#include "lo-error.h"
#include "quit.h"
#include "oct-locbuf.h"

#include "Sparse.h"
#include "sparse-sort.h"
#include "sparse-util.h"
#include "oct-spparms.h"
#include "mx-inlines.cc"

#include "PermMatrix.h"

template <class T>
Sparse<T>::Sparse (const PermMatrix& a)
  : rep (new typename Sparse<T>::SparseRep (a.rows (), a.cols (), a.rows ())),
         dimensions (dim_vector (a.rows (), a.cols()))
{
  octave_idx_type n = a.rows ();
  for (octave_idx_type i = 0; i <= n; i++)
    cidx (i) = i;

  const Array<octave_idx_type> pv = a.pvec ();

  if (a.is_row_perm ())
    {
      for (octave_idx_type i = 0; i < n; i++)
        ridx (pv (i)) = i;
    }
  else
    {
      for (octave_idx_type i = 0; i < n; i++)
        ridx (i) = pv (i);
    }

  for (octave_idx_type i = 0; i < n; i++)
    data (i) = 1.0;
}

template <class T>
T&
Sparse<T>::SparseRep::elem (octave_idx_type _r, octave_idx_type _c)
{
  octave_idx_type i;

  if (nzmx > 0)
    {
      for (i = c[_c]; i < c[_c + 1]; i++)
        if (r[i] == _r)
          return d[i];
        else if (r[i] > _r)
          break;

      // Ok, If we've gotten here, we're in trouble.. Have to create a
      // new element in the sparse array. This' gonna be slow!!!
      if (c[ncols] == nzmx)
        {
          (*current_liboctave_error_handler)
            ("Sparse::SparseRep::elem (octave_idx_type, octave_idx_type): sparse matrix filled");
          return *d;
        }

      octave_idx_type to_move = c[ncols] - i;
      if (to_move != 0)
        {
          for (octave_idx_type j = c[ncols]; j > i; j--)
            {
              d[j] = d[j-1];
              r[j] = r[j-1];
            }
        }

      for (octave_idx_type j = _c + 1; j < ncols + 1; j++)
        c[j] = c[j] + 1;

      d[i] = 0.;
      r[i] = _r;

      return d[i];
    }
  else
    {
      (*current_liboctave_error_handler)
        ("Sparse::SparseRep::elem (octave_idx_type, octave_idx_type): sparse matrix filled");
      return *d;
    }
}

template <class T>
T
Sparse<T>::SparseRep::celem (octave_idx_type _r, octave_idx_type _c) const
{
  if (nzmx > 0)
    for (octave_idx_type i = c[_c]; i < c[_c + 1]; i++)
      if (r[i] == _r)
        return d[i];
  return T ();
}

template <class T>
void
Sparse<T>::SparseRep::maybe_compress (bool remove_zeros)
{
  if (remove_zeros)
    {
      octave_idx_type i = 0, k = 0;
      for (octave_idx_type j = 1; j <= ncols; j++)
        {
          octave_idx_type u = c[j];
          for (i = i; i < u; i++)
            if (d[i] != T())
              {
                d[k] = d[i];
                r[k++] = r[i];
              }
          c[j] = k;
        }
    }

  change_length (c[ncols]);
}

template <class T>
void
Sparse<T>::SparseRep::change_length (octave_idx_type nz)
{
  for (octave_idx_type j = ncols; j > 0 && c[j] > nz; j--)
    c[j] = nz;

  // We shall skip reallocation if we have less than 1/frac extra elements to
  // discard.
  static const int frac = 5;
  if (nz > nzmx || nz < nzmx - nzmx/frac)
    {
      // Reallocate.
      octave_idx_type min_nzmx = std::min (nz, nzmx);

      octave_idx_type * new_ridx = new octave_idx_type [nz];
      copy_or_memcpy (min_nzmx, r, new_ridx);

      delete [] r;
      r = new_ridx;

      T * new_data = new T [nz];
      copy_or_memcpy (min_nzmx, d, new_data);

      delete [] d;
      d = new_data;

      nzmx = nz;
    }
}

template <class T>
bool
Sparse<T>::SparseRep::indices_ok (void) const
{
  return sparse_indices_ok (r, c, nrows, ncols, nnz ());
}

template <class T>
Sparse<T>::Sparse (octave_idx_type nr, octave_idx_type nc, T val)
  : rep (0), dimensions (dim_vector (nr, nc))
{
  if (val != T ())
    {
      rep = new typename Sparse<T>::SparseRep (nr, nc, nr*nc);

      octave_idx_type ii = 0;
      xcidx (0) = 0;
      for (octave_idx_type j = 0; j < nc; j++)
        {
          for (octave_idx_type i = 0; i < nr; i++)
            {
              xdata (ii) = val;
              xridx (ii++) = i;
            }
          xcidx (j+1) = ii;
        }
    }
  else
    {
      rep = new typename Sparse<T>::SparseRep (nr, nc, 0);
      for (octave_idx_type j = 0; j < nc+1; j++)
        xcidx(j) = 0;
    }
}

template <class T>
Sparse<T>::Sparse (const dim_vector& dv)
  : rep (0), dimensions (dv)
{
  if (dv.length() != 2)
    (*current_liboctave_error_handler)
      ("Sparse::Sparse (const dim_vector&): dimension mismatch");
  else
    rep = new typename Sparse<T>::SparseRep (dv(0), dv(1));
}

template <class T>
Sparse<T>::Sparse (const Sparse<T>& a, const dim_vector& dv)
  : rep (0), dimensions (dv)
{

  // Work in unsigned long long to avoid overflow issues with numel
  unsigned long long a_nel = static_cast<unsigned long long>(a.rows ()) *
    static_cast<unsigned long long>(a.cols ());
  unsigned long long dv_nel = static_cast<unsigned long long>(dv (0)) *
    static_cast<unsigned long long>(dv (1));

  if (a_nel != dv_nel)
    (*current_liboctave_error_handler)
      ("Sparse::Sparse (const Sparse&, const dim_vector&): dimension mismatch");
  else
    {
      dim_vector old_dims = a.dims();
      octave_idx_type new_nzmx = a.nnz ();
      octave_idx_type new_nr = dv (0);
      octave_idx_type new_nc = dv (1);
      octave_idx_type old_nr = old_dims (0);
      octave_idx_type old_nc = old_dims (1);

      rep = new typename Sparse<T>::SparseRep (new_nr, new_nc, new_nzmx);

      octave_idx_type kk = 0;
      xcidx(0) = 0;
      for (octave_idx_type i = 0; i < old_nc; i++)
        for (octave_idx_type j = a.cidx(i); j < a.cidx(i+1); j++)
          {
            octave_idx_type tmp = i * old_nr + a.ridx(j);
            octave_idx_type ii = tmp % new_nr;
            octave_idx_type jj = (tmp - ii) / new_nr;
            for (octave_idx_type k = kk; k < jj; k++)
              xcidx(k+1) = j;
            kk = jj;
            xdata(j) = a.data(j);
            xridx(j) = ii;
          }
      for (octave_idx_type k = kk; k < new_nc; k++)
        xcidx(k+1) = new_nzmx;
    }
}

template <class T>
Sparse<T>::Sparse (const Array<T>& a, const idx_vector& r,
                   const idx_vector& c, octave_idx_type nr,
                   octave_idx_type nc, bool sum_terms,
                   octave_idx_type nzm)
  : rep (0), dimensions ()
{
  if (nr < 0)
    nr = r.extent (0);
  else if (r.extent (nr) > nr)
    (*current_liboctave_error_handler) ("sparse: row index %d out of bound %d",
                                        r.extent (nr), nr);

  if (nc < 0)
    nc = c.extent (0);
  else if (c.extent (nc) > nc)
    (*current_liboctave_error_handler)
      ("sparse: column index %d out of bound %d", r.extent (nc), nc);

  rep = new SparseRep (nr, nc);

  dimensions = dim_vector (nr, nc);


  octave_idx_type n = a.numel (), rl = r.length (nr), cl = c.length (nc);
  bool a_scalar = n == 1;
  if (a_scalar)
    {
      if (rl != 1)
        n = rl;
      else if (cl != 1)
        n = cl;
    }

  if ((rl != 1 && rl != n) || (cl != 1 && cl != n))
    (*current_liboctave_error_handler) ("sparse: dimension mismatch");

  if (rl <= 1 && cl <= 1)
    {
      if (n == 1 && a(0) != T ())
        {
          change_capacity (nzm > 1 ? nzm : 1);
          xridx(0) = r(0);
          xdata(0) = a(0);
          for (octave_idx_type j = 0; j < nc; j++)
            xcidx(j+1) = j >= c(0);
        }
    }
  else if (a_scalar)
    {
      // This is completely specialized, because the sorts can be simplified.
      T a0 = a(0);
      if (a0 == T())
        {
          // Do nothing, it's an empty matrix.
        }
      else if (cl == 1)
        {
          // Sparse column vector. Sort row indices.
          idx_vector rs = r.sorted ();

          octave_quit ();

          const octave_idx_type *rd = rs.raw ();
          // Count unique indices.
          octave_idx_type new_nz = 1;
          for (octave_idx_type i = 1; i < n; i++)
            new_nz += rd[i-1] != rd[i];
          // Allocate result.
          change_capacity (nzm > new_nz ? nzm : new_nz);
          xcidx (1) = new_nz;
          octave_idx_type *rri = ridx ();
          T *rrd = data ();

          octave_quit ();

          octave_idx_type k = -1, l = -1;

          if (sum_terms)
            {
              // Sum repeated indices.
              for (octave_idx_type i = 0; i < n; i++)
                {
                  if (rd[i] != l)
                    {
                      l = rd[i];
                      rri[++k] = rd[i];
                      rrd[k] = a0;
                    }
                  else
                    rrd[k] += a0;
                }
            }
          else
            {
              // Pick the last one.
              for (octave_idx_type i = 0; i < n; i++)
                {
                  if (rd[i] != l)
                    {
                      l = rd[i];
                      rri[++k] = rd[i];
                      rrd[k] = a0;
                    }
                }
            }

        }
      else
        {
          idx_vector rr = r, cc = c;
          const octave_idx_type *rd = rr.raw (), *cd = cc.raw ();
          OCTAVE_LOCAL_BUFFER_INIT (octave_idx_type, ci, nc+1, 0);
          ci[0] = 0;
          // Bin counts of column indices.
          for (octave_idx_type i = 0; i < n; i++)
            ci[cd[i]+1]++;
          // Make them cumulative, shifted one to right.
          for (octave_idx_type i = 1, s = 0; i <= nc; i++)
            {
              octave_idx_type s1 = s + ci[i];
              ci[i] = s;
              s = s1;
            }

          octave_quit ();

          // Bucket sort.
          OCTAVE_LOCAL_BUFFER (octave_idx_type, sidx, n);
          for (octave_idx_type i = 0; i < n; i++)
            if (rl == 1)
              sidx[ci[cd[i]+1]++] = rd[0];
            else
              sidx[ci[cd[i]+1]++] = rd[i];

          // Subsorts. We don't need a stable sort, all values are equal.
          xcidx(0) = 0;
          for (octave_idx_type j = 0; j < nc; j++)
            {
              std::sort (sidx + ci[j], sidx + ci[j+1]);
              octave_idx_type l = -1, nzj = 0;
              // Count.
              for (octave_idx_type i = ci[j]; i < ci[j+1]; i++)
                {
                  octave_idx_type k = sidx[i];
                  if (k != l)
                    {
                      l = k;
                      nzj++;
                    }
                }
              // Set column pointer.
              xcidx(j+1) = xcidx(j) + nzj;
            }

          change_capacity (nzm > xcidx (nc) ? nzm : xcidx (nc));
          octave_idx_type *rri = ridx ();
          T *rrd = data ();

          // Fill-in data.
          for (octave_idx_type j = 0, jj = -1; j < nc; j++)
            {
              octave_quit ();
              octave_idx_type l = -1;
              if (sum_terms)
                {
                  // Sum adjacent terms.
                  for (octave_idx_type i = ci[j]; i < ci[j+1]; i++)
                    {
                      octave_idx_type k = sidx[i];
                      if (k != l)
                        {
                          l = k;
                          rrd[++jj] = a0;
                          rri[jj] = k;
                        }
                      else
                        rrd[jj] += a0;
                    }
                }
              else
                {
                  // Use the last one.
                  for (octave_idx_type i = ci[j]; i < ci[j+1]; i++)
                    {
                      octave_idx_type k = sidx[i];
                      if (k != l)
                        {
                          l = k;
                          rrd[++jj] = a0;
                          rri[jj] = k;
                        }
                    }
                }
            }
        }
    }
  else if (cl == 1)
    {
      // Sparse column vector. Sort row indices.
      Array<octave_idx_type> rsi;
      idx_vector rs = r.sorted (rsi);

      octave_quit ();

      const octave_idx_type *rd = rs.raw (), *rdi = rsi.data ();
      // Count unique indices.
      octave_idx_type new_nz = 1;
      for (octave_idx_type i = 1; i < n; i++)
        new_nz += rd[i-1] != rd[i];
      // Allocate result.
      change_capacity (nzm > new_nz ? nzm : new_nz);
      xcidx(1) = new_nz;
      octave_idx_type *rri = ridx ();
      T *rrd = data ();

      octave_quit ();

      octave_idx_type k = 0;
      rri[k] = rd[0];
      rrd[k] = a(rdi[0]);

      if (sum_terms)
        {
          // Sum repeated indices.
          for (octave_idx_type i = 1; i < n; i++)
            {
              if (rd[i] != rd[i-1])
                {
                  rri[++k] = rd[i];
                  rrd[k] = a(rdi[i]);
                }
              else
                rrd[k] += a(rdi[i]);
            }
        }
      else
        {
          // Pick the last one.
          for (octave_idx_type i = 1; i < n; i++)
            {
              if (rd[i] != rd[i-1])
                rri[++k] = rd[i];
              rrd[k] = a(rdi[i]);
            }
        }

      maybe_compress (true);
    }
  else
    {
      idx_vector rr = r, cc = c;
      const octave_idx_type *rd = rr.raw (), *cd = cc.raw ();
      OCTAVE_LOCAL_BUFFER_INIT (octave_idx_type, ci, nc+1, 0);
      ci[0] = 0;
      // Bin counts of column indices.
      for (octave_idx_type i = 0; i < n; i++)
        ci[cd[i]+1]++;
      // Make them cumulative, shifted one to right.
      for (octave_idx_type i = 1, s = 0; i <= nc; i++)
        {
          octave_idx_type s1 = s + ci[i];
          ci[i] = s;
          s = s1;
        }

      octave_quit ();

      typedef std::pair<octave_idx_type, octave_idx_type> idx_pair;
      // Bucket sort.
      OCTAVE_LOCAL_BUFFER (idx_pair, spairs, n);
      for (octave_idx_type i = 0; i < n; i++)
        {
          idx_pair& p = spairs[ci[cd[i]+1]++];
          if (rl == 1)
            p.first = rd[0];
          else
            p.first = rd[i];
          p.second = i;
        }

      // Subsorts. We don't need a stable sort, the second index stabilizes it.
      xcidx(0) = 0;
      for (octave_idx_type j = 0; j < nc; j++)
        {
          std::sort (spairs + ci[j], spairs + ci[j+1]);
          octave_idx_type l = -1, nzj = 0;
          // Count.
          for (octave_idx_type i = ci[j]; i < ci[j+1]; i++)
            {
              octave_idx_type k = spairs[i].first;
              if (k != l)
                {
                  l = k;
                  nzj++;
                }
            }
          // Set column pointer.
          xcidx(j+1) = xcidx(j) + nzj;
        }

      change_capacity (nzm > xcidx (nc) ? nzm : xcidx (nc));
      octave_idx_type *rri = ridx ();
      T *rrd = data ();

      // Fill-in data.
      for (octave_idx_type j = 0, jj = -1; j < nc; j++)
        {
          octave_quit ();
          octave_idx_type l = -1;
          if (sum_terms)
            {
              // Sum adjacent terms.
              for (octave_idx_type i = ci[j]; i < ci[j+1]; i++)
                {
                  octave_idx_type k = spairs[i].first;
                  if (k != l)
                    {
                      l = k;
                      rrd[++jj] = a(spairs[i].second);
                      rri[jj] = k;
                    }
                  else
                    rrd[jj] += a(spairs[i].second);
                }
            }
          else
            {
              // Use the last one.
              for (octave_idx_type i = ci[j]; i < ci[j+1]; i++)
                {
                  octave_idx_type k = spairs[i].first;
                  if (k != l)
                    {
                      l = k;
                      rri[++jj] = k;
                    }
                  rrd[jj] = a(spairs[i].second);
                }
            }
        }

      maybe_compress (true);
    }
}

template <class T>
Sparse<T>::Sparse (const Array<T>& a)
  : rep (0), dimensions (a.dims ())
{
  if (dimensions.length () > 2)
    (*current_liboctave_error_handler)
      ("Sparse::Sparse (const Array<T>&): dimension mismatch");
  else
    {
      octave_idx_type nr = rows ();
      octave_idx_type nc = cols ();
      octave_idx_type len = a.length ();
      octave_idx_type new_nzmx = 0;

      // First count the number of non-zero terms
      for (octave_idx_type i = 0; i < len; i++)
        if (a(i) != T ())
          new_nzmx++;

      rep = new typename Sparse<T>::SparseRep (nr, nc, new_nzmx);

      octave_idx_type ii = 0;
      xcidx(0) = 0;
      for (octave_idx_type j = 0; j < nc; j++)
        {
          for (octave_idx_type i = 0; i < nr; i++)
            if (a.elem (i,j) != T ())
              {
                xdata(ii) = a.elem (i,j);
                xridx(ii++) = i;
              }
          xcidx(j+1) = ii;
        }
    }
}

template <class T>
Sparse<T>::~Sparse (void)
{
  if (--rep->count == 0)
    delete rep;
}

template <class T>
Sparse<T>&
Sparse<T>::operator = (const Sparse<T>& a)
{
  if (this != &a)
    {
      if (--rep->count == 0)
        delete rep;

      rep = a.rep;
      rep->count++;

      dimensions = a.dimensions;
    }

  return *this;
}

template <class T>
octave_idx_type
Sparse<T>::compute_index (const Array<octave_idx_type>& ra_idx) const
{
  octave_idx_type retval = -1;

  octave_idx_type n = dimensions.length ();

  if (n > 0 && n == ra_idx.length ())
    {
      retval = ra_idx(--n);

      while (--n >= 0)
        {
          retval *= dimensions(n);
          retval += ra_idx(n);
        }
    }
  else
    (*current_liboctave_error_handler)
      ("Sparse<T>::compute_index: invalid ra_idxing operation");

  return retval;
}

template <class T>
T
Sparse<T>::range_error (const char *fcn, octave_idx_type n) const
{
  (*current_liboctave_error_handler) ("%s (%d): range error", fcn, n);
  return T ();
}

template <class T>
T&
Sparse<T>::range_error (const char *fcn, octave_idx_type n)
{
  (*current_liboctave_error_handler) ("%s (%d): range error", fcn, n);
  static T foo;
  return foo;
}

template <class T>
T
Sparse<T>::range_error (const char *fcn, octave_idx_type i, octave_idx_type j) const
{
  (*current_liboctave_error_handler)
    ("%s (%d, %d): range error", fcn, i, j);
  return T ();
}

template <class T>
T&
Sparse<T>::range_error (const char *fcn, octave_idx_type i, octave_idx_type j)
{
  (*current_liboctave_error_handler)
    ("%s (%d, %d): range error", fcn, i, j);
  static T foo;
  return foo;
}

template <class T>
T
Sparse<T>::range_error (const char *fcn, const Array<octave_idx_type>& ra_idx) const
{
  std::ostringstream buf;

  buf << fcn << " (";

  octave_idx_type n = ra_idx.length ();

  if (n > 0)
    buf << ra_idx(0);

  for (octave_idx_type i = 1; i < n; i++)
    buf << ", " << ra_idx(i);

  buf << "): range error";

  std::string buf_str = buf.str ();

  (*current_liboctave_error_handler) (buf_str.c_str ());

  return T ();
}

template <class T>
T&
Sparse<T>::range_error (const char *fcn, const Array<octave_idx_type>& ra_idx)
{
  std::ostringstream buf;

  buf << fcn << " (";

  octave_idx_type n = ra_idx.length ();

  if (n > 0)
    buf << ra_idx(0);

  for (octave_idx_type i = 1; i < n; i++)
    buf << ", " << ra_idx(i);

  buf << "): range error";

  std::string buf_str = buf.str ();

  (*current_liboctave_error_handler) (buf_str.c_str ());

  static T foo;
  return foo;
}

template <class T>
Sparse<T>
Sparse<T>::reshape (const dim_vector& new_dims) const
{
  Sparse<T> retval;
  dim_vector dims2 = new_dims;

  if (dims2.length () > 2)
    {
      (*current_liboctave_warning_handler)
        ("reshape: sparse reshape to N-d array smashes dims");

      for (octave_idx_type i = 2; i < dims2.length(); i++)
        dims2(1) *= dims2(i);

      dims2.resize (2);
    }

  if (dimensions != dims2)
    {
      if (dimensions.numel () == dims2.numel ())
        {
          octave_idx_type new_nnz = nnz ();
          octave_idx_type new_nr = dims2 (0);
          octave_idx_type new_nc = dims2 (1);
          octave_idx_type old_nr = rows ();
          octave_idx_type old_nc = cols ();
          retval = Sparse<T> (new_nr, new_nc, new_nnz);

          octave_idx_type kk = 0;
          retval.xcidx(0) = 0;
          for (octave_idx_type i = 0; i < old_nc; i++)
            for (octave_idx_type j = cidx(i); j < cidx(i+1); j++)
              {
                octave_idx_type tmp = i * old_nr + ridx(j);
                octave_idx_type ii = tmp % new_nr;
                octave_idx_type jj = (tmp - ii) / new_nr;
                for (octave_idx_type k = kk; k < jj; k++)
                  retval.xcidx(k+1) = j;
                kk = jj;
                retval.xdata(j) = data(j);
                retval.xridx(j) = ii;
              }
          for (octave_idx_type k = kk; k < new_nc; k++)
            retval.xcidx(k+1) = new_nnz;
        }
      else
        {
          std::string dimensions_str = dimensions.str ();
          std::string new_dims_str = new_dims.str ();

          (*current_liboctave_error_handler)
            ("reshape: can't reshape %s array to %s array",
             dimensions_str.c_str (), new_dims_str.c_str ());
        }
    }
  else
    retval = *this;

  return retval;
}

template <class T>
Sparse<T>
Sparse<T>::permute (const Array<octave_idx_type>& perm_vec, bool) const
{
  // The only valid permutations of a sparse array are [1, 2] and [2, 1].

  bool fail = false;
  bool trans = false;

  if (perm_vec.length () == 2)
    {
      if (perm_vec(0) == 0 && perm_vec(1) == 1)
        /* do nothing */;
      else if (perm_vec(0) == 1 && perm_vec(1) == 0)
        trans = true;
      else
        fail = true;
    }
  else
    fail = true;

  if (fail)
    (*current_liboctave_error_handler)
      ("permutation vector contains an invalid element");

  return trans ? this->transpose () : *this;
}

template <class T>
void
Sparse<T>::resize1 (octave_idx_type n)
{
  octave_idx_type nr = rows (), nc = cols ();

  if (nr == 0)
    resize (1, std::max (nc, n));
  else if (nc == 0)
    resize (nr, (n + nr - 1) / nr); // Ain't it wicked?
  else if (nr == 1)
    resize (1, n);
  else if (nc == 1)
    resize (n, 1);
  else
    gripe_invalid_resize ();
}

template <class T>
void
Sparse<T>::resize (const dim_vector& dv)
{
  octave_idx_type n = dv.length ();

  if (n != 2)
    {
      (*current_liboctave_error_handler) ("sparse array must be 2-D");
      return;
    }

  resize (dv(0), dv(1));
}

template <class T>
void
Sparse<T>::resize (octave_idx_type r, octave_idx_type c)
{
  if (r < 0 || c < 0)
    {
      (*current_liboctave_error_handler)
        ("can't resize to negative dimension");
      return;
    }

  if (r == dim1 () && c == dim2 ())
    return;

  // This wouldn't be necessary for r >= rows () if nrows wasn't part of the
  // Sparse rep. It is not good for anything in there.
  make_unique ();

  if (r < rows ())
    {
      octave_idx_type i = 0, k = 0;
      for (octave_idx_type j = 1; j <= rep->ncols; j++)
        {
          octave_idx_type u = xcidx(j);
          for (i = i; i < u; i++)
            if (xridx(i) < r)
              {
                xdata(k) = xdata(i);
                xridx(k++) = xridx(i);
              }
          xcidx(j) = k;
        }
    }

  rep->nrows = dimensions(0) = r;

  if (c != rep->ncols)
    {
      octave_idx_type *new_cidx = new octave_idx_type [c+1];
      copy_or_memcpy (std::min (c, rep->ncols)+1, rep->c, new_cidx);
      delete [] rep->c;
      rep->c = new_cidx;

      if (c > rep->ncols)
        fill_or_memset (c - rep->ncols, rep->c[rep->ncols], rep->c + rep->ncols + 1);
    }

  rep->ncols = dimensions(1) = c;

  rep->change_length (rep->nnz ());
}

template <class T>
Sparse<T>&
Sparse<T>::insert (const Sparse<T>& a, octave_idx_type r, octave_idx_type c)
{
  octave_idx_type a_rows = a.rows ();
  octave_idx_type a_cols = a.cols ();
  octave_idx_type nr = rows ();
  octave_idx_type nc = cols ();

  if (r < 0 || r + a_rows > rows () || c < 0 || c + a_cols > cols ())
    {
      (*current_liboctave_error_handler) ("range error for insert");
      return *this;
    }

  // First count the number of elements in the final array
  octave_idx_type nel = cidx(c) + a.nnz ();

  if (c + a_cols < nc)
    nel += cidx(nc) - cidx(c + a_cols);

  for (octave_idx_type i = c; i < c + a_cols; i++)
    for (octave_idx_type j = cidx(i); j < cidx(i+1); j++)
      if (ridx(j) < r || ridx(j) >= r + a_rows)
        nel++;

  Sparse<T> tmp (*this);
  --rep->count;
  rep = new typename Sparse<T>::SparseRep (nr, nc, nel);

  for (octave_idx_type i = 0; i < tmp.cidx(c); i++)
    {
      data(i) = tmp.data(i);
      ridx(i) = tmp.ridx(i);
    }
  for (octave_idx_type i = 0; i < c + 1; i++)
    cidx(i) = tmp.cidx(i);

  octave_idx_type ii = cidx(c);

  for (octave_idx_type i = c; i < c + a_cols; i++)
    {
      octave_quit ();

      for (octave_idx_type j = tmp.cidx(i); j < tmp.cidx(i+1); j++)
        if (tmp.ridx(j) < r)
          {
            data(ii) = tmp.data(j);
            ridx(ii++) = tmp.ridx(j);
          }

      octave_quit ();

      for (octave_idx_type j = a.cidx(i-c); j < a.cidx(i-c+1); j++)
        {
          data(ii) = a.data(j);
          ridx(ii++) = r + a.ridx(j);
        }

      octave_quit ();

      for (octave_idx_type j = tmp.cidx(i); j < tmp.cidx(i+1); j++)
        if (tmp.ridx(j) >= r + a_rows)
          {
            data(ii) = tmp.data(j);
            ridx(ii++) = tmp.ridx(j);
          }

      cidx(i+1) = ii;
    }

  for (octave_idx_type i = c + a_cols; i < nc; i++)
    {
      for (octave_idx_type j = tmp.cidx(i); j < tmp.cidx(i+1); j++)
        {
          data(ii) = tmp.data(j);
          ridx(ii++) = tmp.ridx(j);
        }
      cidx(i+1) = ii;
    }

  return *this;
}

template <class T>
Sparse<T>&
Sparse<T>::insert (const Sparse<T>& a, const Array<octave_idx_type>& ra_idx)
{

  if (ra_idx.length () != 2)
    {
      (*current_liboctave_error_handler) ("range error for insert");
      return *this;
    }

  return insert (a, ra_idx (0), ra_idx (1));
}

template <class T>
Sparse<T>
Sparse<T>::transpose (void) const
{
  assert (ndims () == 2);

  octave_idx_type nr = rows ();
  octave_idx_type nc = cols ();
  octave_idx_type nz = nnz ();
  Sparse<T> retval (nc, nr, nz);

  for (octave_idx_type i = 0; i < nz; i++)
    retval.xcidx (ridx (i) + 1)++;
  // retval.xcidx[1:nr] holds the row degrees for rows 0:(nr-1)
  nz = 0;
  for (octave_idx_type i = 1; i <= nr; i++)
    {
      const octave_idx_type tmp = retval.xcidx (i);
      retval.xcidx (i) = nz;
      nz += tmp;
    }
  // retval.xcidx[1:nr] holds row entry *start* offsets for rows 0:(nr-1)

  for (octave_idx_type j = 0; j < nc; j++)
    for (octave_idx_type k = cidx(j); k < cidx(j+1); k++)
      {
        octave_idx_type q = retval.xcidx (ridx (k) + 1)++;
        retval.xridx (q) = j;
        retval.xdata (q) = data (k);
      }
  assert (nnz () == retval.xcidx (nr));
  // retval.xcidx[1:nr] holds row entry *end* offsets for rows 0:(nr-1)
  // and retval.xcidx[0:(nr-1)] holds their row entry *start* offsets

  return retval;
}

// Lower bound lookup. Could also use octave_sort, but that has upper bound
// semantics, so requires some manipulation to set right. Uses a plain loop for
// small columns.
static octave_idx_type
lblookup (const octave_idx_type *ridx, octave_idx_type nr,
          octave_idx_type ri)
{
  if (nr <= 8)
    {
      octave_idx_type l;
      for (l = 0; l < nr; l++)
        if (ridx[l] >= ri)
          break;
      return l;
    }
  else
    return std::lower_bound (ridx, ridx + nr, ri) - ridx;
}

template <class T>
void
Sparse<T>::delete_elements (const idx_vector& idx)
{
  Sparse<T> retval;

  assert (ndims () == 2);

  octave_idx_type nr = dim1 ();
  octave_idx_type nc = dim2 ();
  octave_idx_type nz = nnz ();

  octave_idx_type nel = numel (); // Can throw.

  const dim_vector idx_dims = idx.orig_dimensions ();

  if (idx.extent (nel) > nel)
    gripe_del_index_out_of_range (true, idx.extent (nel), nel);
  else if (nc == 1)
    {
      // Sparse column vector.
      const Sparse<T> tmp = *this; // constant copy to prevent COW.

      octave_idx_type lb, ub;

      if (idx.is_cont_range (nel, lb, ub))
        {
          // Special-case a contiguous range.
          // Look-up indices first.
          octave_idx_type li = lblookup (tmp.ridx (), nz, lb);
          octave_idx_type ui = lblookup (tmp.ridx (), nz, ub);
          // Copy data and adjust indices.
          octave_idx_type nz_new = nz - (ui - li);
          *this = Sparse<T> (nr - (ub - lb), 1, nz_new);
          copy_or_memcpy (li, tmp.data (), data ());
          copy_or_memcpy (li, tmp.ridx (), xridx ());
          copy_or_memcpy (nz - ui, tmp.data () + ui, xdata () + li);
          mx_inline_sub (nz - ui, xridx () + li, tmp.ridx () + ui, ub - lb);
          xcidx(1) = nz_new;
        }
      else
        {
          OCTAVE_LOCAL_BUFFER (octave_idx_type, ridx_new, nz);
          OCTAVE_LOCAL_BUFFER (T, data_new, nz);
          idx_vector sidx = idx.sorted (true);
          const octave_idx_type *sj = sidx.raw ();
          octave_idx_type sl = sidx.length (nel), nz_new = 0, j = 0;
          for (octave_idx_type i = 0; i < nz; i++)
            {
              octave_idx_type r = tmp.ridx(i);
              for (;j < sl && sj[j] < r; j++) ;
              if (j == sl || sj[j] > r)
                {
                  data_new[nz_new] = tmp.data(i);
                  ridx_new[nz_new++] = r - j;
                }
            }

          *this = Sparse<T> (nr - sl, 1, nz_new);
          copy_or_memcpy (nz_new, ridx_new, ridx ());
          copy_or_memcpy (nz_new, data_new, xdata ());
          xcidx(1) = nz_new;
        }
    }
  else if (nr == 1)
    {
      // Sparse row vector.
      octave_idx_type lb, ub;
      if (idx.is_cont_range (nc, lb, ub))
        {
          const Sparse<T> tmp = *this;
          octave_idx_type lbi = tmp.cidx(lb), ubi = tmp.cidx(ub), new_nz = nz - (ubi - lbi);
          *this = Sparse<T> (1, nc - (ub - lb), new_nz);
          copy_or_memcpy (lbi, tmp.data (), data ());
          copy_or_memcpy (nz - ubi, tmp.data () + ubi, xdata () + lbi);
          fill_or_memset (new_nz, static_cast<octave_idx_type> (0), ridx ());
          copy_or_memcpy (lb, tmp.cidx () + 1, cidx () + 1);
          mx_inline_sub (nc - ub, xcidx () + 1, tmp.cidx () + ub + 1, ubi - lbi);
        }
      else
        *this = index (idx.complement (nc));
    }
  else
    {
      *this = index (idx_vector::colon);
      delete_elements (idx);
      *this = transpose (); // We want a row vector.
    }
}

template <class T>
void
Sparse<T>::delete_elements (const idx_vector& idx_i, const idx_vector& idx_j)
{
  assert (ndims () == 2);

  octave_idx_type nr = dim1 ();
  octave_idx_type nc = dim2 ();
  octave_idx_type nz = nnz ();

  if (idx_i.is_colon ())
    {
      // Deleting columns.
      octave_idx_type lb, ub;
      if (idx_j.extent (nc) > nc)
        gripe_del_index_out_of_range (false, idx_j.extent (nc), nc);
      else if (idx_j.is_cont_range (nc, lb, ub))
        {
          const Sparse<T> tmp = *this;
          octave_idx_type lbi = tmp.cidx(lb), ubi = tmp.cidx(ub), new_nz = nz - (ubi - lbi);
          *this = Sparse<T> (nr, nc - (ub - lb), new_nz);
          copy_or_memcpy (lbi, tmp.data (), data ());
          copy_or_memcpy (lbi, tmp.ridx (), ridx ());
          copy_or_memcpy (nz - ubi, tmp.data () + ubi, xdata () + lbi);
          copy_or_memcpy (nz - ubi, tmp.ridx () + ubi, xridx () + lbi);
          copy_or_memcpy (lb, tmp.cidx () + 1, cidx () + 1);
          mx_inline_sub (nc - ub, xcidx () + 1, tmp.cidx () + ub + 1, ubi - lbi);
        }
      else
        *this = index (idx_i, idx_j.complement (nc));
    }
  else if (idx_j.is_colon ())
    {
      // Deleting rows.
      octave_idx_type lb, ub;
      if (idx_i.extent (nr) > nr)
        gripe_del_index_out_of_range (false, idx_i.extent (nr), nr);
      else if (idx_i.is_cont_range (nr, lb, ub))
        {
          // This is more memory-efficient than the approach below.
          const Sparse<T> tmpl = index (idx_vector (0, lb), idx_j);
          const Sparse<T> tmpu = index (idx_vector (ub, nr), idx_j);
          *this = Sparse<T> (nr - (ub - lb), nc, tmpl.nnz () + tmpu.nnz ());
          for (octave_idx_type j = 0, k = 0; j < nc; j++)
            {
              for (octave_idx_type i = tmpl.cidx(j); i < tmpl.cidx(j+1); i++)
                {
                  xdata(k) = tmpl.data(i);
                  xridx(k++) = tmpl.ridx(i);
                }
              for (octave_idx_type i = tmpu.cidx(j); i < tmpu.cidx(j+1); i++)
                {
                  xdata(k) = tmpu.data(i);
                  xridx(k++) = tmpu.ridx(i) + lb;
                }

              xcidx(j+1) = k;
            }
        }
      else
        {
          // This is done by transposing, deleting columns, then transposing
          // again.
          Sparse<T> tmp = transpose ();
          tmp.delete_elements (idx_j, idx_i);
          *this = tmp.transpose ();
        }
    }
  else
    (*current_liboctave_error_handler)
      ("a null assignment can only have one non-colon index");
}

template <class T>
void
Sparse<T>::delete_elements (int dim, const idx_vector& idx)
{
  if (dim == 0)
    delete_elements (idx, idx_vector::colon);
  else if (dim == 1)
    delete_elements (idx_vector::colon, idx);
  else
    {
      (*current_liboctave_error_handler)
        ("invalid dimension in delete_elements");
      return;
    }
}

template <class T>
Sparse<T>
Sparse<T>::index (const idx_vector& idx, bool resize_ok) const
{
  Sparse<T> retval;

  assert (ndims () == 2);

  octave_idx_type nr = dim1 ();
  octave_idx_type nc = dim2 ();
  octave_idx_type nz = nnz ();

  octave_idx_type nel = numel (); // Can throw.

  const dim_vector idx_dims = idx.orig_dimensions ();

  if (idx_dims.length () > 2)
    (*current_liboctave_error_handler)
      ("cannot index sparse matrix with an N-D Array");
  else if (idx.is_colon ())
    {
      if (nc == 1)
        retval = *this;
      else
        {
          // Fast magic colon processing.
          retval = Sparse<T> (nel, 1, nz);

          for (octave_idx_type i = 0; i < nc; i++)
            {
              for (octave_idx_type j = cidx(i); j < cidx(i+1); j++)
                {
                  retval.xdata(j) = data(j);
                  retval.xridx(j) = ridx(j) + i * nr;
                }
            }

          retval.xcidx(0) = 0;
          retval.xcidx(1) = nz;
        }
    }
  else if (idx.extent (nel) > nel)
    {
      // resize_ok is completely handled here.
      if (resize_ok)
        {
          octave_idx_type ext = idx.extent (nel);
          Sparse<T> tmp = *this;
          tmp.resize1 (ext);
          retval = tmp.index (idx);
        }
      else
        gripe_index_out_of_range (1, 1, idx.extent (nel), nel);
    }
  else if (nr == 1 && nc == 1)
    {
      // You have to be pretty sick to get to this bit of code,
      // since you have a scalar stored as a sparse matrix, and
      // then want to make a dense matrix with sparse
      // representation. Ok, we'll do it, but you deserve what
      // you get!!
      retval = Sparse<T> (idx_dims(0), idx_dims(1), nz ? data(0) : T ());
    }
  else if (nc == 1)
    {
      // Sparse column vector.
      octave_idx_type lb, ub;

      if (idx.is_scalar ())
        {
          // Scalar index - just a binary lookup.
          octave_idx_type i = lblookup (ridx (), nz, idx(0));
          if (i < nz && ridx(i) == idx(0))
            retval = Sparse (1, 1, data(i));
          else
            retval = Sparse (1, 1);
        }
      else if (idx.is_cont_range (nel, lb, ub))
        {
          // Special-case a contiguous range.
          // Look-up indices first.
          octave_idx_type li = lblookup (ridx (), nz, lb);
          octave_idx_type ui = lblookup (ridx (), nz, ub);
          // Copy data and adjust indices.
          octave_idx_type nz_new = ui - li;
          retval = Sparse<T> (ub - lb, 1, nz_new);
          copy_or_memcpy (nz_new, data () + li, retval.data ());
          mx_inline_sub (nz_new, retval.xridx (), ridx () + li, lb);
          retval.xcidx(1) = nz_new;
        }
      else if (idx.is_permutation (nel) && idx.is_vector ())
        {
          if (idx.is_range () && idx.increment () == -1)
            {
              retval = Sparse<T> (nr, 1, nz);
              std::reverse_copy (ridx (), ridx () + nz, retval.ridx ());
              std::reverse_copy (data (), data () + nz, retval.data ());
            }
          else
            {
              Array<T> tmp = array_value ();
              tmp = tmp.index (idx);
              retval = Sparse<T> (tmp);
            }
        }
      else
        {
          // If indexing a sparse column vector by a vector, the result is a
          // sparse column vector, otherwise it inherits the shape of index.
          // Vector transpose is cheap, so do it right here.
          const Array<octave_idx_type> idxa = (idx_dims(0) == 1
                                               ? idx.as_array ().transpose ()
                                               : idx.as_array ());

          octave_idx_type new_nr = idxa.rows (), new_nc = idxa.cols ();

          // Lookup.
          // FIXME: Could specialize for sorted idx?
          NoAlias< Array<octave_idx_type> > lidx (dim_vector (new_nr, new_nc));
          for (octave_idx_type i = 0; i < new_nr*new_nc; i++)
            lidx(i) = lblookup (ridx (), nz, idxa(i));

          // Count matches.
          retval = Sparse<T> (idxa.rows (), idxa.cols ());
          for (octave_idx_type j = 0; j < new_nc; j++)
            {
              octave_idx_type nzj = 0;
              for (octave_idx_type i = 0; i < new_nr; i++)
                {
                  octave_idx_type l = lidx(i, j);
                  if (l < nz && ridx(l) == idxa(i, j))
                    nzj++;
                  else
                    lidx(i, j) = nz;
                }
              retval.xcidx(j+1) = retval.xcidx(j) + nzj;
            }

          retval.change_capacity (retval.xcidx(new_nc));

          // Copy data and set row indices.
          octave_idx_type k = 0;
          for (octave_idx_type j = 0; j < new_nc; j++)
            for (octave_idx_type i = 0; i < new_nr; i++)
              {
                octave_idx_type l = lidx(i, j);
                if (l < nz)
                  {
                    retval.data(k) = data(l);
                    retval.xridx(k++) = i;
                  }
              }
        }
    }
  else if (nr == 1)
    {
      octave_idx_type lb, ub;
      if (idx.is_scalar ())
        retval = Sparse<T> (1, 1, elem(0, idx(0)));
      else if (idx.is_cont_range (nel, lb, ub))
        {
          // Special-case a contiguous range.
          octave_idx_type lbi = cidx(lb), ubi = cidx(ub), new_nz = ubi - lbi;
          retval = Sparse<T> (1, ub - lb, new_nz);
          copy_or_memcpy (new_nz, data () + lbi, retval.data ());
          fill_or_memset (new_nz, static_cast<octave_idx_type> (0), retval.ridx ());
          mx_inline_sub (ub - lb + 1, retval.cidx (), cidx () + lb, lbi);
        }
      else
        {
          // Sparse row vectors occupy O(nr) storage anyway, so let's just
          // convert the matrix to full, index, and sparsify the result.
          retval = Sparse<T> (array_value ().index (idx));
        }
    }
  else
    {
      if (nr != 0 && idx.is_scalar ())
        retval = Sparse<T> (1, 1, elem (idx(0) % nr, idx(0) / nr));
      else
        {
          // Indexing a non-vector sparse matrix by linear indexing.
          // I suppose this is rare (and it may easily overflow), so let's take the easy way,
          // and reshape first to column vector, which is already handled above.
          retval = index (idx_vector::colon).index (idx);
          // In this case we're supposed to always inherit the shape, but column(row) doesn't do
          // it, so we'll do it instead.
          if (idx_dims(0) == 1 && idx_dims(1) != 1)
            retval = retval.transpose ();
        }
    }

  return retval;
}

template <class T>
Sparse<T>
Sparse<T>::index (const idx_vector& idx_i, const idx_vector& idx_j, bool resize_ok) const
{
  Sparse<T> retval;

  assert (ndims () == 2);

  octave_idx_type nr = dim1 ();
  octave_idx_type nc = dim2 ();

  octave_idx_type n = idx_i.length (nr);
  octave_idx_type m = idx_j.length (nc);

  octave_idx_type lb, ub;

  if (idx_i.extent (nr) > nr || idx_j.extent (nc) > nc)
    {
      // resize_ok is completely handled here.
      if (resize_ok)
        {
          octave_idx_type ext_i = idx_i.extent (nr);
          octave_idx_type ext_j = idx_j.extent (nc);
          Sparse<T> tmp = *this;
          tmp.resize (ext_i, ext_j);
          retval = tmp.index (idx_i, idx_j);
        }
      else if (idx_i.extent (nr) > nr)
        gripe_index_out_of_range (2, 1, idx_i.extent (nr), nr);
      else
        gripe_index_out_of_range (2, 2, idx_j.extent (nc), nc);
    }
  else if (idx_i.is_colon ())
    {
      // Great, we're just manipulating columns. This is going to be quite
      // efficient, because the columns can stay compressed as they are.
      if (idx_j.is_colon ())
        retval = *this; // Shallow copy.
      else if (idx_j.is_cont_range (nc, lb, ub))
        {
          // Special-case a contiguous range.
          octave_idx_type lbi = cidx(lb), ubi = cidx(ub), new_nz = ubi - lbi;
          retval = Sparse<T> (nr, ub - lb, new_nz);
          copy_or_memcpy (new_nz, data () + lbi, retval.data ());
          copy_or_memcpy (new_nz, ridx () + lbi, retval.ridx ());
          mx_inline_sub (ub - lb + 1, retval.cidx (), cidx () + lb, lbi);
        }
      else
        {
          // Count new nonzero elements.
          retval = Sparse<T> (nr, m);
          for (octave_idx_type j = 0; j < m; j++)
            {
              octave_idx_type jj = idx_j(j);
              retval.xcidx(j+1) = retval.xcidx(j) + (cidx(jj+1) - cidx(jj));
            }

          retval.change_capacity (retval.xcidx (m));

          // Copy data & indices.
          for (octave_idx_type j = 0; j < m; j++)
            {
              octave_idx_type ljj = cidx(idx_j(j));
              octave_idx_type lj = retval.xcidx(j), nzj = retval.xcidx(j+1) - lj;
              copy_or_memcpy (nzj, data () + ljj, retval.data () + lj);
              copy_or_memcpy (nzj, ridx () + ljj, retval.ridx () + lj);
            }
        }
    }
  else if (nc == 1 && idx_j.is_colon_equiv (nc) && idx_i.is_vector ())
    {
      // It's actually vector indexing. The 1D index is specialized for that.
      retval = index (idx_i);
    }
  else if (idx_i.is_scalar ())
    {
      octave_idx_type ii = idx_i(0);
      retval = Sparse<T> (1, m);
      OCTAVE_LOCAL_BUFFER (octave_idx_type, ij, m);
      for (octave_idx_type j = 0; j < m; j++)
        {
          octave_quit ();
          octave_idx_type jj = idx_j(j), lj = cidx(jj), nzj = cidx(jj+1) - cidx(jj);
          // Scalar index - just a binary lookup.
          octave_idx_type i = lblookup (ridx () + lj, nzj, ii);
          if (i < nzj && ridx(i+lj) == ii)
            {
              ij[j] = i + lj;
              retval.xcidx(j+1) = retval.xcidx(j) + 1;
            }
          else
            retval.xcidx(j+1) = retval.xcidx(j);
        }

      retval.change_capacity (retval.xcidx(m));

      // Copy data, adjust row indices.
      for (octave_idx_type j = 0; j < m; j++)
        {
          octave_idx_type i = retval.xcidx(j);
          if (retval.xcidx(j+1) > i)
            {
              retval.xridx(i) = 0;
              retval.xdata(i) = data(ij[j]);
            }
        }
    }
  else if (idx_i.is_cont_range (nr, lb, ub))
    {
      retval = Sparse<T> (n, m);
      OCTAVE_LOCAL_BUFFER (octave_idx_type, li, m);
      OCTAVE_LOCAL_BUFFER (octave_idx_type, ui, m);
      for (octave_idx_type j = 0; j < m; j++)
        {
          octave_quit ();
          octave_idx_type jj = idx_j(j), lj = cidx(jj), nzj = cidx(jj+1) - cidx(jj);
          octave_idx_type lij, uij;
          // Lookup indices.
          li[j] = lij = lblookup (ridx () + lj, nzj, lb) + lj;
          ui[j] = uij = lblookup (ridx () + lj, nzj, ub) + lj;
          retval.xcidx(j+1) = retval.xcidx(j) + ui[j] - li[j];
        }

      retval.change_capacity (retval.xcidx(m));

      // Copy data, adjust row indices.
      for (octave_idx_type j = 0, k = 0; j < m; j++)
        {
          octave_quit ();
          for (octave_idx_type i = li[j]; i < ui[j]; i++)
            {
              retval.xdata(k) = data(i);
              retval.xridx(k++) = ridx(i) - lb;
            }
        }
    }
  else if (idx_i.is_permutation (nr))
    {
      // The columns preserve their length, we just need to renumber and sort them.
      // Count new nonzero elements.
      retval = Sparse<T> (nr, m);
      for (octave_idx_type j = 0; j < m; j++)
        {
          octave_idx_type jj = idx_j(j);
          retval.xcidx(j+1) = retval.xcidx(j) + (cidx(jj+1) - cidx(jj));
        }

      retval.change_capacity (retval.xcidx (m));

      octave_quit ();

      if (idx_i.is_range () && idx_i.increment () == -1)
        {
          // It's nr:-1:1. Just flip all columns.
          for (octave_idx_type j = 0; j < m; j++)
            {
              octave_quit ();
              octave_idx_type jj = idx_j(j), lj = cidx(jj), nzj = cidx(jj+1) - cidx(jj);
              octave_idx_type li = retval.xcidx(j), uj = lj + nzj - 1;
              for (octave_idx_type i = 0; i < nzj; i++)
                {
                  retval.xdata(li + i) = data(uj - i); // Copy in reverse order.
                  retval.xridx(li + i) = nr - 1 - ridx(uj - i); // Ditto with transform.
                }
            }
        }
      else
        {
          // Get inverse permutation.
          idx_vector idx_iinv = idx_i.inverse_permutation (nr);
          const octave_idx_type *iinv = idx_iinv.raw ();

          // Scatter buffer.
          OCTAVE_LOCAL_BUFFER (T, scb, nr);
          octave_idx_type *rri = retval.ridx ();

          for (octave_idx_type j = 0; j < m; j++)
            {
              octave_quit ();
              octave_idx_type jj = idx_j(j), lj = cidx(jj), nzj = cidx(jj+1) - cidx(jj);
              octave_idx_type li = retval.xcidx(j);
              // Scatter the column, transform indices.
              for (octave_idx_type i = 0; i < nzj; i++)
                scb[rri[li + i] = iinv[ridx(lj + i)]] = data(lj + i);

              octave_quit ();

              // Sort them.
              std::sort (rri + li, rri + li + nzj);

              // Gather.
              for (octave_idx_type i = 0; i < nzj; i++)
                retval.xdata(li + i) = scb[rri[li + i]];
            }
        }

    }
  else if (idx_j.is_colon ())
    {
      // This requires  uncompressing columns, which is generally costly,
      // so we rely on the efficient transpose to handle this.
      // It may still make sense to optimize some cases here.
      retval = transpose ();
      retval = retval.index (idx_vector::colon, idx_i);
      retval = retval.transpose ();
    }
  else
    {
      // A(I, J) is decomposed into A(:, J)(I, :).
      retval = index (idx_vector::colon, idx_j);
      retval = retval.index (idx_i, idx_vector::colon);
    }

  return retval;
}

template <class T>
void
Sparse<T>::assign (const idx_vector& idx, const Sparse<T>& rhs)
{
  Sparse<T> retval;

  assert (ndims () == 2);

  octave_idx_type nr = dim1 ();
  octave_idx_type nc = dim2 ();
  octave_idx_type nz = nnz ();

  octave_idx_type n = numel (); // Can throw.

  octave_idx_type rhl = rhs.numel ();

  if (idx.length (n) == rhl)
    {
      if (rhl == 0)
        return;

      octave_idx_type nx = idx.extent (n);
      // Try to resize first if necessary.
      if (nx != n)
        {
          resize1 (nx);
          n = numel ();
          nr = rows ();
          nc = cols ();
          // nz is preserved.
        }

      if (idx.is_colon ())
        {
          *this = rhs.reshape (dimensions);
        }
      else if (nc == 1 && rhs.cols () == 1)
        {
          // Sparse column vector to sparse column vector assignment.

          octave_idx_type lb, ub;
          if (idx.is_cont_range (nr, lb, ub))
            {
              // Special-case a contiguous range.
              // Look-up indices first.
              octave_idx_type li = lblookup (ridx (), nz, lb);
              octave_idx_type ui = lblookup (ridx (), nz, ub);
              octave_idx_type rnz = rhs.nnz (), new_nz = nz - (ui - li) + rnz;

              if (new_nz >= nz && new_nz <= capacity ())
                {
                  // Adding/overwriting elements, enough capacity allocated.

                  if (new_nz > nz)
                    {
                      // Make room first.
                      std::copy_backward (data () + ui, data () + nz, data () + nz + rnz);
                      std::copy_backward (ridx () + ui, ridx () + nz, ridx () + nz + rnz);
                    }

                  // Copy data and adjust indices from rhs.
                  copy_or_memcpy (rnz, rhs.data (), data () + li);
                  mx_inline_add (rnz, ridx () + li, rhs.ridx (), lb);
                }
              else
                {
                  // Clearing elements or exceeding capacity, allocate afresh
                  // and paste pieces.
                  const Sparse<T> tmp = *this;
                  *this = Sparse<T> (nr, 1, new_nz);

                  // Head ...
                  copy_or_memcpy (li, tmp.data (), data ());
                  copy_or_memcpy (li, tmp.ridx (), ridx ());

                  // new stuff ...
                  copy_or_memcpy (rnz, rhs.data (), data () + li);
                  mx_inline_add (rnz, ridx () + li, rhs.ridx (), lb);

                  // ...tail
                  copy_or_memcpy (nz - ui, tmp.data () + ui, data () + li + rnz);
                  copy_or_memcpy (nz - ui, tmp.ridx () + ui, ridx () + li + rnz);
                }

              cidx(1) = new_nz;
            }
          else if (idx.is_range () && idx.increment () == -1)
            {
              // It's s(u:-1:l) = r. Reverse the assignment.
              assign (idx.sorted (), rhs.index (idx_vector (rhl - 1, 0, -1)));
            }
          else if (idx.is_permutation (n))
            {
              *this = rhs.index (idx.inverse_permutation (n));
            }
          else if (rhs.nnz () == 0)
            {
              // Elements are being zeroed.
              octave_idx_type *ri = ridx ();
              for (octave_idx_type i = 0; i < rhl; i++)
                {
                  octave_idx_type iidx = idx(i);
                  octave_idx_type li = lblookup (ri, nz, iidx);
                  if (li != nz && ri[li] == iidx)
                    xdata(li) = T();
                }

              maybe_compress (true);
            }
          else
            {
              const Sparse<T> tmp = *this;
              octave_idx_type new_nz = nz + rhl;
              // Disassembly our matrix...
              Array<octave_idx_type> new_ri (dim_vector (new_nz, 1));
              Array<T> new_data (dim_vector (new_nz, 1));
              copy_or_memcpy (nz, tmp.ridx (), new_ri.fortran_vec ());
              copy_or_memcpy (nz, tmp.data (), new_data.fortran_vec ());
              // ... insert new data (densified) ...
              idx.copy_data (new_ri.fortran_vec () + nz);
              new_data.assign (idx_vector (nz, new_nz), rhs.array_value ());
              // ... reassembly.
              *this = Sparse<T> (new_data, new_ri,
                                 static_cast<octave_idx_type> (0),
                                 nr, nc, false);
            }
        }
      else
        {
          dim_vector save_dims = dimensions;
          *this = index (idx_vector::colon);
          assign (idx, rhs.index (idx_vector::colon));
          *this = reshape (save_dims);
        }
    }
  else if (rhl == 1)
    {
      rhl = idx.length (n);
      if (rhs.nnz () != 0)
        assign (idx, Sparse<T> (rhl, 1, rhs.data (0)));
      else
        assign (idx, Sparse<T> (rhl, 1));
    }
  else
    gripe_invalid_assignment_size ();
}

template <class T>
void
Sparse<T>::assign (const idx_vector& idx_i,
                   const idx_vector& idx_j, const Sparse<T>& rhs)
{
  Sparse<T> retval;

  assert (ndims () == 2);

  octave_idx_type nr = dim1 ();
  octave_idx_type nc = dim2 ();
  octave_idx_type nz = nnz ();

  octave_idx_type n = rhs.rows ();
  octave_idx_type m = rhs.columns ();

  // FIXME -- this should probably be written more like the
  // Array<T>::assign function...

  bool orig_zero_by_zero = (nr == 0 && nc == 0);

  if (orig_zero_by_zero || (idx_i.length (nr) == n && idx_j.length (nc) == m))
    {
      octave_idx_type nrx;
      octave_idx_type ncx;

      if (orig_zero_by_zero)
        {
          if (idx_i.is_colon ())
            {
              nrx = n;

              if (idx_j.is_colon ())
                ncx = m;
              else
                ncx = idx_j.extent (nc);
            }
          else if (idx_j.is_colon ())
            {
              nrx = idx_i.extent (nr);
              ncx = m;
            }
          else
            {
              nrx = idx_i.extent (nr);
              ncx = idx_j.extent (nc);
            }
        }
      else
        {
          nrx = idx_i.extent (nr);
          ncx = idx_j.extent (nc);
        }

      // Try to resize first if necessary.
      if (nrx != nr || ncx != nc)
        {
          resize (nrx, ncx);
          nr = rows ();
          nc = cols ();
          // nz is preserved.
        }

      if (n == 0 || m == 0)
        return;

      if (idx_i.is_colon ())
        {
          octave_idx_type lb, ub;
          // Great, we're just manipulating columns. This is going to be quite
          // efficient, because the columns can stay compressed as they are.
          if (idx_j.is_colon ())
            *this = rhs; // Shallow copy.
          else if (idx_j.is_cont_range (nc, lb, ub))
            {
              // Special-case a contiguous range.
              octave_idx_type li = cidx(lb), ui = cidx(ub);
              octave_idx_type rnz = rhs.nnz (), new_nz = nz - (ui - li) + rnz;

              if (new_nz >= nz && new_nz <= capacity ())
                {
                  // Adding/overwriting elements, enough capacity allocated.

                  if (new_nz > nz)
                    {
                      // Make room first.
                      std::copy (data () + ui, data () + nz,
                                 data () + li + rnz);
                      std::copy (ridx () + ui, ridx () + nz,
                                 ridx () + li + rnz);
                      mx_inline_add2 (nc - ub, cidx () + ub + 1, new_nz - nz);
                    }

                  // Copy data and indices from rhs.
                  copy_or_memcpy (rnz, rhs.data (), data () + li);
                  copy_or_memcpy (rnz, rhs.ridx (), ridx () + li);
                  mx_inline_add (ub - lb, cidx () + lb + 1, rhs.cidx () + 1, li);

                  assert (nnz () == new_nz);
                }
              else
                {
                  // Clearing elements or exceeding capacity, allocate afresh
                  // and paste pieces.
                  const Sparse<T> tmp = *this;
                  *this = Sparse<T> (nr, nc, new_nz);

                  // Head...
                  copy_or_memcpy (li, tmp.data (), data ());
                  copy_or_memcpy (li, tmp.ridx (), ridx ());
                  copy_or_memcpy (lb, tmp.cidx () + 1, cidx () + 1);

                  // new stuff...
                  copy_or_memcpy (rnz, rhs.data (), data () + li);
                  copy_or_memcpy (rnz, rhs.ridx (), ridx () + li);
                  mx_inline_add (ub - lb, cidx () + lb + 1, rhs.cidx () + 1, li);

                  // ...tail.
                  copy_or_memcpy (nz - ui, tmp.data () + ui, data () + li + rnz);
                  copy_or_memcpy (nz - ui, tmp.ridx () + ui, ridx () + li + rnz);
                  mx_inline_add (nc - ub, cidx () + ub + 1, tmp.cidx () + ub + 1, new_nz - nz);

                  assert (nnz () == new_nz);
                }
            }
          else if (idx_j.is_range () && idx_j.increment () == -1)
            {
              // It's s(:,u:-1:l) = r. Reverse the assignment.
              assign (idx_i, idx_j.sorted (), rhs.index (idx_i, idx_vector (m - 1, 0, -1)));
            }
          else if (idx_j.is_permutation (nc))
            {
              *this = rhs.index (idx_i, idx_j.inverse_permutation (nc));
            }
          else
            {
              const Sparse<T> tmp = *this;
              *this = Sparse<T> (nr, nc);
              OCTAVE_LOCAL_BUFFER_INIT (octave_idx_type, jsav, nc, -1);

              // Assemble column lengths.
              for (octave_idx_type i = 0; i < nc; i++)
                xcidx(i+1) = tmp.cidx(i+1) - tmp.cidx(i);

              for (octave_idx_type i = 0; i < m; i++)
                {
                  octave_idx_type j =idx_j(i);
                  jsav[j] = i;
                  xcidx(j+1) = rhs.cidx(i+1) - rhs.cidx(i);
                }

              // Make cumulative.
              for (octave_idx_type i = 0; i < nc; i++)
                xcidx(i+1) += xcidx(i);

              change_capacity (nnz ());

              // Merge columns.
              for (octave_idx_type i = 0; i < nc; i++)
                {
                  octave_idx_type l = xcidx(i), u = xcidx(i+1), j = jsav[i];
                  if (j >= 0)
                    {
                      // from rhs
                      octave_idx_type k = rhs.cidx(j);
                      copy_or_memcpy (u - l, rhs.data () + k, xdata () + l);
                      copy_or_memcpy (u - l, rhs.ridx () + k, xridx () + l);
                    }
                  else
                    {
                      // original
                      octave_idx_type k = tmp.cidx(i);
                      copy_or_memcpy (u - l, tmp.data () + k, xdata () + l);
                      copy_or_memcpy (u - l, tmp.ridx () + k, xridx () + l);
                    }
                }

            }
        }
      else if (nc == 1 && idx_j.is_colon_equiv (nc) && idx_i.is_vector ())
        {
          // It's actually vector indexing. The 1D assign is specialized for that.
          assign (idx_i, rhs);
        }
      else if (idx_j.is_colon ())
        {
          if (idx_i.is_permutation (nr))
            {
              *this = rhs.index (idx_i.inverse_permutation (nr), idx_j);
            }
          else
            {
              // FIXME: optimize more special cases?
              // In general this requires unpacking the columns, which is slow,
              // especially for many small columns. OTOH, transpose is an
              // efficient O(nr+nc+nnz) operation.
              *this = transpose ();
              assign (idx_vector::colon, idx_i, rhs.transpose ());
              *this = transpose ();
            }
        }
      else
        {
          // Split it into 2 assignments and one indexing.
          Sparse<T> tmp = index (idx_vector::colon, idx_j);
          tmp.assign (idx_i, idx_vector::colon, rhs);
          assign (idx_vector::colon, idx_j, tmp);
        }
    }
  else if (m == 1 && n == 1)
    {
      n = idx_i.length (nr);
      m = idx_j.length (nc);
      if (rhs.nnz () != 0)
        assign (idx_i, idx_j, Sparse<T> (n, m, rhs.data (0)));
      else
        assign (idx_i, idx_j, Sparse<T> (n, m));
    }
  else
    gripe_assignment_dimension_mismatch ();
}

// Can't use versions of these in Array.cc due to duplication of the
// instantiations for Array<double and Sparse<double>, etc
template <class T>
bool
sparse_ascending_compare (typename ref_param<T>::type a,
                          typename ref_param<T>::type b)
{
  return (a < b);
}

template <class T>
bool
sparse_descending_compare (typename ref_param<T>::type a,
                           typename ref_param<T>::type b)
{
  return (a > b);
}

template <class T>
Sparse<T>
Sparse<T>::sort (octave_idx_type dim, sortmode mode) const
{
  Sparse<T> m = *this;

  octave_idx_type nr = m.rows ();
  octave_idx_type nc = m.columns ();

  if (m.length () < 1 || dim > 1)
    return m;

  if (dim > 0)
    {
      m = m.transpose ();
      nr = m.rows ();
      nc = m.columns ();
    }

  octave_sort<T> lsort;

  if (mode == ASCENDING)
    lsort.set_compare (sparse_ascending_compare<T>);
  else if (mode == DESCENDING)
    lsort.set_compare (sparse_descending_compare<T>);
  else
    abort ();

  T *v = m.data ();
  octave_idx_type *mcidx = m.cidx ();
  octave_idx_type *mridx = m.ridx ();

  for (octave_idx_type j = 0; j < nc; j++)
    {
      octave_idx_type ns = mcidx [j + 1] - mcidx [j];
      lsort.sort (v, ns);

      octave_idx_type i;
      if (mode == ASCENDING)
        {
          for (i = 0; i < ns; i++)
            if (sparse_ascending_compare<T> (static_cast<T> (0), v [i]))
              break;
        }
      else
        {
          for (i = 0; i < ns; i++)
            if (sparse_descending_compare<T> (static_cast<T> (0), v [i]))
              break;
        }
      for (octave_idx_type k = 0; k < i; k++)
        mridx [k] = k;
      for (octave_idx_type k = i; k < ns; k++)
        mridx [k] = k - ns + nr;

      v += ns;
      mridx += ns;
    }

  if (dim > 0)
      m = m.transpose ();

  return m;
}

template <class T>
Sparse<T>
Sparse<T>::sort (Array<octave_idx_type> &sidx, octave_idx_type dim,
                 sortmode mode) const
{
  Sparse<T> m = *this;

  octave_idx_type nr = m.rows ();
  octave_idx_type nc = m.columns ();

  if (m.length () < 1 || dim > 1)
    {
      sidx = Array<octave_idx_type> (dim_vector (nr, nc), 1);
      return m;
    }

  if (dim > 0)
    {
      m = m.transpose ();
      nr = m.rows ();
      nc = m.columns ();
    }

  octave_sort<T> indexed_sort;

  if (mode == ASCENDING)
    indexed_sort.set_compare (sparse_ascending_compare<T>);
  else if (mode == DESCENDING)
    indexed_sort.set_compare (sparse_descending_compare<T>);
  else
    abort ();

  T *v = m.data ();
  octave_idx_type *mcidx = m.cidx ();
  octave_idx_type *mridx = m.ridx ();

  sidx = Array<octave_idx_type> (dim_vector (nr, nc));
  OCTAVE_LOCAL_BUFFER (octave_idx_type, vi, nr);

  for (octave_idx_type j = 0; j < nc; j++)
    {
      octave_idx_type ns = mcidx [j + 1] - mcidx [j];
      octave_idx_type offset = j * nr;

      if (ns == 0)
        {
          for (octave_idx_type k = 0; k < nr; k++)
            sidx (offset + k) = k;
        }
      else
        {
          for (octave_idx_type i = 0; i < ns; i++)
            vi[i] = mridx[i];

          indexed_sort.sort (v, vi, ns);

          octave_idx_type i;
          if (mode == ASCENDING)
            {
              for (i = 0; i < ns; i++)
                if (sparse_ascending_compare<T> (static_cast<T> (0), v[i]))
                  break;
            }
          else
            {
              for (i = 0; i < ns; i++)
                if (sparse_descending_compare<T> (static_cast<T> (0), v[i]))
                  break;
            }

          octave_idx_type ii = 0;
          octave_idx_type jj = i;
          for (octave_idx_type k = 0; k < nr; k++)
            {
              if (ii < ns && mridx[ii] == k)
                ii++;
              else
                sidx (offset + jj++) = k;
            }

          for (octave_idx_type k = 0; k < i; k++)
            {
              sidx (k + offset) = vi [k];
              mridx [k] = k;
            }

          for (octave_idx_type k = i; k < ns; k++)
            {
              sidx (k - ns + nr + offset) = vi [k];
              mridx [k] = k - ns + nr;
            }

          v += ns;
          mridx += ns;
        }
    }

  if (dim > 0)
    {
      m = m.transpose ();
      sidx = sidx.transpose ();
    }

  return m;
}

template <class T>
Sparse<T>
Sparse<T>::diag (octave_idx_type k) const
{
  octave_idx_type nnr = rows ();
  octave_idx_type nnc = cols ();
  Sparse<T> d;

  if (nnr == 0 || nnc == 0)
    ; // do nothing
  else if (nnr != 1 && nnc != 1)
    {
      if (k > 0)
        nnc -= k;
      else if (k < 0)
        nnr += k;

      if (nnr > 0 && nnc > 0)
        {
          octave_idx_type ndiag = (nnr < nnc) ? nnr : nnc;

          // Count the number of non-zero elements
          octave_idx_type nel = 0;
          if (k > 0)
            {
              for (octave_idx_type i = 0; i < ndiag; i++)
                if (elem (i, i+k) != 0.)
                  nel++;
            }
          else if ( k < 0)
            {
              for (octave_idx_type i = 0; i < ndiag; i++)
                if (elem (i-k, i) != 0.)
                  nel++;
            }
          else
            {
              for (octave_idx_type i = 0; i < ndiag; i++)
                if (elem (i, i) != 0.)
                  nel++;
            }

          d = Sparse<T> (ndiag, 1, nel);
          d.xcidx (0) = 0;
          d.xcidx (1) = nel;

          octave_idx_type ii = 0;
          if (k > 0)
            {
              for (octave_idx_type i = 0; i < ndiag; i++)
                {
                  T tmp = elem (i, i+k);
                  if (tmp != 0.)
                    {
                      d.xdata (ii) = tmp;
                      d.xridx (ii++) = i;
                    }
                }
            }
          else if ( k < 0)
            {
              for (octave_idx_type i = 0; i < ndiag; i++)
                {
                  T tmp = elem (i-k, i);
                  if (tmp != 0.)
                    {
                      d.xdata (ii) = tmp;
                      d.xridx (ii++) = i;
                    }
                }
            }
          else
            {
              for (octave_idx_type i = 0; i < ndiag; i++)
                {
                  T tmp = elem (i, i);
                  if (tmp != 0.)
                    {
                      d.xdata (ii) = tmp;
                      d.xridx (ii++) = i;
                    }
                }
            }
        }
      else
        (*current_liboctave_error_handler)
          ("diag: requested diagonal out of range");
    }
  else if (nnr != 0 && nnc != 0)
    {
      octave_idx_type roff = 0;
      octave_idx_type coff = 0;
      if (k > 0)
        {
          roff = 0;
          coff = k;
        }
      else if (k < 0)
        {
          roff = -k;
          coff = 0;
        }

      if (nnr == 1)
        {
          octave_idx_type n = nnc + std::abs (k);
          octave_idx_type nz = nnz ();

          d = Sparse<T> (n, n, nz);

          if (nnz () > 0)
            {
              for (octave_idx_type i = 0; i < coff+1; i++)
                d.xcidx (i) = 0;

              for (octave_idx_type j = 0; j < nnc; j++)
                {
                  for (octave_idx_type i = cidx(j); i < cidx(j+1); i++)
                    {
                      d.xdata (i) = data (i);
                      d.xridx (i) = j + roff;
                    }
                  d.xcidx (j + coff + 1) = cidx(j+1);
                }

              for (octave_idx_type i = nnc + coff + 1; i < n + 1; i++)
                d.xcidx (i) = nz;
            }
        }
      else
        {
          octave_idx_type n = nnr + std::abs (k);
          octave_idx_type nz = nnz ();

          d = Sparse<T> (n, n, nz);

          if (nnz () > 0)
            {
              octave_idx_type ii = 0;
              octave_idx_type ir = ridx(0);

              for (octave_idx_type i = 0; i < coff+1; i++)
                d.xcidx (i) = 0;

              for (octave_idx_type i = 0; i < nnr; i++)
                {
                  if (ir == i)
                    {
                      d.xdata (ii) = data (ii);
                      d.xridx (ii++) = ir + roff;

                      if (ii != nz)
                        ir = ridx (ii);
                    }
                  d.xcidx (i + coff + 1) = ii;
                }

              for (octave_idx_type i = nnr + coff + 1; i < n+1; i++)
                d.xcidx (i) = nz;
            }
        }
    }

  return d;
}

template <class T>
Sparse<T>
Sparse<T>::cat (int dim, octave_idx_type n, const Sparse<T> *sparse_list)
{
  // Default concatenation.
  bool (dim_vector::*concat_rule) (const dim_vector&, int) = &dim_vector::concat;

  if (dim == -1 || dim == -2)
    {
      concat_rule = &dim_vector::hvcat;
      dim = -dim - 1;
    }
  else if (dim < 0)
    (*current_liboctave_error_handler)
      ("cat: invalid dimension");

  dim_vector dv;
  octave_idx_type total_nz = 0;
  if (dim == 0 || dim == 1)
    {
      if (n == 1)
        return sparse_list[0];

      for (octave_idx_type i = 0; i < n; i++)
        {
          if (! (dv.*concat_rule) (sparse_list[i].dims (), dim))
            (*current_liboctave_error_handler)
              ("cat: dimension mismatch");
          total_nz += sparse_list[i].nnz ();
        }
    }
  else
    (*current_liboctave_error_handler)
      ("cat: invalid dimension for sparse concatenation");

  Sparse<T> retval (dv, total_nz);

  if (retval.is_empty ())
    return retval;

  switch (dim)
    {
    case 0:
      {
        // sparse vertcat. This is not efficiently handled by assignment, so
        // we'll do it directly.
        octave_idx_type l = 0;
        for (octave_idx_type j = 0; j < dv(1); j++)
          {
            octave_quit ();

            octave_idx_type rcum = 0;
            for (octave_idx_type i = 0; i < n; i++)
              {
                const Sparse<T>& spi = sparse_list[i];
                // Skipping empty matrices. See the comment in Array.cc.
                if (spi.is_empty ())
                  continue;

                octave_idx_type kl = spi.cidx(j), ku = spi.cidx(j+1);
                for (octave_idx_type k = kl; k < ku; k++, l++)
                  {
                    retval.xridx(l) = spi.ridx(k) + rcum;
                    retval.xdata(l) = spi.data(k);
                  }

                rcum += spi.rows ();
              }

            retval.xcidx(j+1) = l;
          }

        break;
      }
    case 1:
      {
        octave_idx_type l = 0;
        for (octave_idx_type i = 0; i < n; i++)
          {
            octave_quit ();

            // Skipping empty matrices. See the comment in Array.cc.
            if (sparse_list[i].is_empty ())
              continue;

            octave_idx_type u = l + sparse_list[i].columns ();
            retval.assign (idx_vector::colon, idx_vector (l, u), sparse_list[i]);
            l = u;
          }

        break;
      }
    default:
      assert (false);
    }

  return retval;
}

template <class T>
Array<T>
Sparse<T>::array_value () const
{
  NoAlias< Array<T> > retval (dims (), T());
  if (rows () == 1)
    {
      octave_idx_type i = 0;
      for (octave_idx_type j = 0, nc = cols (); j < nc; j++)
        {
          if (cidx(j+1) > i)
            retval(j) = data (i++);
        }
    }
  else
    {
      for (octave_idx_type j = 0, nc = cols (); j < nc; j++)
        for (octave_idx_type i = cidx(j), iu = cidx(j+1); i < iu; i++)
          retval (ridx(i), j) = data (i);
    }

  return retval;
}

/*
 * Tests
 *

%!function x = set_slice(x, dim, slice, arg)
%!  switch dim
%!    case 11
%!      x(slice) = 2;
%!    case 21
%!      x(slice, :) = 2;
%!    case 22
%!      x(:, slice) = 2;
%!    otherwise
%!      error("invalid dim, '%d'", dim);
%!  endswitch
%! endfunction

%!function x = set_slice2(x, dim, slice)
%!  switch dim
%!    case 11
%!      x(slice) = 2 * ones (size(slice));
%!    case 21
%!      x(slice, :) = 2 * ones (length(slice), columns (x));
%!    case 22
%!      x(:, slice) = 2 * ones (rows (x), length(slice));
%!    otherwise
%!      error("invalid dim, '%d'", dim);
%!  endswitch
%! endfunction

%!function test_sparse_slice(size, dim, slice)
%!  x = ones(size);
%!  s = set_slice(sparse(x), dim, slice);
%!  f = set_slice(x, dim, slice);
%!  assert (nnz(s), nnz(f));
%!  assert(full(s), f);
%!  s = set_slice2(sparse(x), dim, slice);
%!  f = set_slice2(x, dim, slice);
%!  assert (nnz(s), nnz(f));
%!  assert(full(s), f);
%! endfunction

#### 1d indexing

## size = [2 0]
%!test test_sparse_slice([2 0], 11, []);
%!assert(set_slice(sparse(ones([2 0])), 11, 1), sparse([2 0]'));  # sparse different from full
%!assert(set_slice(sparse(ones([2 0])), 11, 2), sparse([0 2]'));  # sparse different from full
%!assert(set_slice(sparse(ones([2 0])), 11, 3), sparse([0 0; 2 0]'));  # sparse different from full
%!assert(set_slice(sparse(ones([2 0])), 11, 4), sparse([0 0; 0 2]'));  # sparse different from full

## size = [0 2]
%!test test_sparse_slice([0 2], 11, []);
%!assert(set_slice(sparse(ones([0 2])), 11, 1), sparse([2 0]));  # sparse different from full
%!test test_sparse_slice([0 2], 11, 2);
%!test test_sparse_slice([0 2], 11, 3);
%!test test_sparse_slice([0 2], 11, 4);
%!test test_sparse_slice([0 2], 11, [4, 4]);

## size = [2 1]
%!test test_sparse_slice([2 1], 11, []);
%!test test_sparse_slice([2 1], 11, 1);
%!test test_sparse_slice([2 1], 11, 2);
%!test test_sparse_slice([2 1], 11, 3);
%!test test_sparse_slice([2 1], 11, 4);
%!test test_sparse_slice([2 1], 11, [4, 4]);

## size = [1 2]
%!test test_sparse_slice([1 2], 11, []);
%!test test_sparse_slice([1 2], 11, 1);
%!test test_sparse_slice([1 2], 11, 2);
%!test test_sparse_slice([1 2], 11, 3);
%!test test_sparse_slice([1 2], 11, 4);
%!test test_sparse_slice([1 2], 11, [4, 4]);

## size = [2 2]
%!test test_sparse_slice([2 2], 11, []);
%!test test_sparse_slice([2 2], 11, 1);
%!test test_sparse_slice([2 2], 11, 2);
%!test test_sparse_slice([2 2], 11, 3);
%!test test_sparse_slice([2 2], 11, 4);
%!test test_sparse_slice([2 2], 11, [4, 4]);
# These 2 errors are the same as in the full case
%!error id=Octave:invalid-resize set_slice(sparse(ones([2 2])), 11, 5);
%!error id=Octave:invalid-resize set_slice(sparse(ones([2 2])), 11, 6);


#### 2d indexing

## size = [2 0]
%!test test_sparse_slice([2 0], 21, []);
%!test test_sparse_slice([2 0], 21, 1);
%!test test_sparse_slice([2 0], 21, 2);
%!test test_sparse_slice([2 0], 21, [2,2]);
%!assert(set_slice(sparse(ones([2 0])), 21, 3), sparse(3,0));
%!assert(set_slice(sparse(ones([2 0])), 21, 4), sparse(4,0));
%!test test_sparse_slice([2 0], 22, []);
%!test test_sparse_slice([2 0], 22, 1);
%!test test_sparse_slice([2 0], 22, 2);
%!test test_sparse_slice([2 0], 22, [2,2]);
%!assert(set_slice(sparse(ones([2 0])), 22, 3), sparse([0 0 2;0 0 2]));  # sparse different from full
%!assert(set_slice(sparse(ones([2 0])), 22, 4), sparse([0 0 0 2;0 0 0 2]));  # sparse different from full

## size = [0 2]
%!test test_sparse_slice([0 2], 21, []);
%!test test_sparse_slice([0 2], 21, 1);
%!test test_sparse_slice([0 2], 21, 2);
%!test test_sparse_slice([0 2], 21, [2,2]);
%!assert(set_slice(sparse(ones([0 2])), 21, 3), sparse([0 0;0 0;2 2]));  # sparse different from full
%!assert(set_slice(sparse(ones([0 2])), 21, 4), sparse([0 0;0 0;0 0;2 2]));  # sparse different from full
%!test test_sparse_slice([0 2], 22, []);
%!test test_sparse_slice([0 2], 22, 1);
%!test test_sparse_slice([0 2], 22, 2);
%!test test_sparse_slice([0 2], 22, [2,2]);
%!assert(set_slice(sparse(ones([0 2])), 22, 3), sparse(0,3));
%!assert(set_slice(sparse(ones([0 2])), 22, 4), sparse(0,4));

## size = [2 1]
%!test test_sparse_slice([2 1], 21, []);
%!test test_sparse_slice([2 1], 21, 1);
%!test test_sparse_slice([2 1], 21, 2);
%!test test_sparse_slice([2 1], 21, [2,2]);
%!test test_sparse_slice([2 1], 21, 3);
%!test test_sparse_slice([2 1], 21, 4);
%!test test_sparse_slice([2 1], 22, []);
%!test test_sparse_slice([2 1], 22, 1);
%!test test_sparse_slice([2 1], 22, 2);
%!test test_sparse_slice([2 1], 22, [2,2]);
%!test test_sparse_slice([2 1], 22, 3);
%!test test_sparse_slice([2 1], 22, 4);

## size = [1 2]
%!test test_sparse_slice([1 2], 21, []);
%!test test_sparse_slice([1 2], 21, 1);
%!test test_sparse_slice([1 2], 21, 2);
%!test test_sparse_slice([1 2], 21, [2,2]);
%!test test_sparse_slice([1 2], 21, 3);
%!test test_sparse_slice([1 2], 21, 4);
%!test test_sparse_slice([1 2], 22, []);
%!test test_sparse_slice([1 2], 22, 1);
%!test test_sparse_slice([1 2], 22, 2);
%!test test_sparse_slice([1 2], 22, [2,2]);
%!test test_sparse_slice([1 2], 22, 3);
%!test test_sparse_slice([1 2], 22, 4);

## size = [2 2]
%!test test_sparse_slice([2 2], 21, []);
%!test test_sparse_slice([2 2], 21, 1);
%!test test_sparse_slice([2 2], 21, 2);
%!test test_sparse_slice([2 2], 21, [2,2]);
%!test test_sparse_slice([2 2], 21, 3);
%!test test_sparse_slice([2 2], 21, 4);
%!test test_sparse_slice([2 2], 22, []);
%!test test_sparse_slice([2 2], 22, 1);
%!test test_sparse_slice([2 2], 22, 2);
%!test test_sparse_slice([2 2], 22, [2,2]);
%!test test_sparse_slice([2 2], 22, 3);
%!test test_sparse_slice([2 2], 22, 4);

*/

template <class T>
void
Sparse<T>::print_info (std::ostream& os, const std::string& prefix) const
{
  os << prefix << "rep address: " << rep << "\n"
     << prefix << "rep->nzmx:   " << rep->nzmx  << "\n"
     << prefix << "rep->nrows:  " << rep->nrows << "\n"
     << prefix << "rep->ncols:  " << rep->ncols << "\n"
     << prefix << "rep->data:   " << static_cast<void *> (rep->d) << "\n"
     << prefix << "rep->ridx:   " << static_cast<void *> (rep->r) << "\n"
     << prefix << "rep->cidx:   " << static_cast<void *> (rep->c) << "\n"
     << prefix << "rep->count:  " << rep->count << "\n";
}

#define INSTANTIATE_SPARSE(T, API) \
  template class API Sparse<T>;