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//
// Copyright (C) 1993-2026 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
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////////////////////////////////////////////////////////////////////////

#if ! defined (octave_Range_h)
#define octave_Range_h 1

#include "octave-config.h"

#include <iosfwd>
#include <type_traits>

#include "Array-fwd.h"
#include "dMatrix.h"
#include "dim-vector.h"
#include "oct-error.h"
#include "oct-sort.h"
#include "range-fwd.h"

OCTAVE_BEGIN_NAMESPACE(octave)

// For now, only define for floating point types.  However, we only
// need range<float> as a temporary local variable in make_float_range
// in ov.cc.

template <typename T>
class range<T, typename std::enable_if<std::is_floating_point<T>::value>::type>
{
public:

  range ()
    : m_base (0), m_increment (0), m_limit (0), m_final (0), m_numel (0),
      m_reverse (false)
  { }

  // LIMIT is an upper limit and may be outside the range of actual
  // values.  For floating point ranges, we perform a tolerant check
  // to attempt to capture limit in the set of values if it is "close"
  // to the value of base + a multiple of the increment.

  range (const T& base, const T& increment, const T& limit,
         bool reverse = false)
    : m_base (base), m_increment (increment), m_limit (limit),
      m_final (), m_numel (), m_reverse (reverse)
  {
    init ();
  }

  range (const T& base, const T& limit)
    : m_base (base), m_increment (1), m_limit (limit), m_final (), m_numel (),
      m_reverse (false)
  {
    init ();
  }

  // Allow conversion from (presumably) properly constructed Range
  // objects.  The values of base, limit, increment, and numel must be
  // consistent.

  // FIXME: Actually check that base, limit, increment, and numel are
  // consistent?

  range (const T& base, const T& increment, const T& limit,
         octave_idx_type numel, bool reverse = false)
    : m_base (base), m_increment (increment), m_limit (limit),
      m_final (limit), m_numel (numel), m_reverse (reverse)
  { }

  // We don't use a constructor for this because it will conflict with
  // range<T> (base, limit, increment) when T is octave_idx_type.

  static range<T> make_n_element_range (const T& base, const T& increment,
                                        octave_idx_type numel,
                                        bool reverse = false)
  {
    // We could just make this constructor public, but it allows
    // inconsistent ranges to be constructed.  And it is probably much
    // clearer to see "make_n_element_range" instead of puzzling over the
    // purpose of this strange constructor form.

    T final_val = (reverse ? base - (numel - 1) * increment
                           : base + (numel - 1) * increment);

    return range<T> (base, increment, final_val, numel, reverse);
  }

  OCTAVE_DEFAULT_COPY_MOVE_DELETE (range)

  T base () const { return m_base; }
  T increment () const { return m_increment; }
  T limit () const { return m_limit; }
  bool reverse () const { return m_reverse; }

  T final_value () const { return m_final; }

  T min () const
  {
    return (m_numel > 0
            ? ((m_reverse ? m_increment > T (0)
                          : m_increment > T (0)) ? base () : final_value ())
            : T (0));
  }

  T max () const
  {
    return (m_numel > 0
            ? ((m_reverse ? m_increment < T (0)
                          : m_increment > T (0)) ? final_value () : base ())
            : T (0));
  }

  octave_idx_type numel () const { return m_numel; }

  // To support things like "for i = 1:Inf; ...; end" that are
  // required for Matlab compatibility, creation of a range object
  // like 1:Inf is allowed with m_numel set to
  // numeric_limits<octave_idx_type>::max().  However, it is not
  // possible to store these ranges.  The following function allows
  // us to easily distinguish ranges with an infinite number of
  // elements.  There are specializations for double and float.

  bool is_storable () const { return true; }

  dim_vector dims () const { return dim_vector (1, m_numel); }

  octave_idx_type rows () const { return 1; }

  octave_idx_type cols () const { return numel (); }
  octave_idx_type columns () const { return numel (); }

  bool isempty () const { return numel () == 0; }

  bool all_elements_are_ints () const { return true; }

  sortmode issorted (sortmode mode = ASCENDING) const
  {
    if (m_numel > 1 && (m_reverse ? m_increment < T (0)
                                  : m_increment > T (0)))
      mode = ((mode == DESCENDING) ? UNSORTED : ASCENDING);
    else if (m_numel > 1 && (m_reverse ? m_increment > T (0)
                                       : m_increment < T (0)))
      mode = ((mode == ASCENDING) ? UNSORTED : DESCENDING);
    else
      mode = ((mode == UNSORTED) ? ASCENDING : mode);

    return mode;
  }

  OCTAVE_API octave_idx_type nnz () const;

  // Support for single-index subscripting, without generating matrix cache.

  T checkelem (octave_idx_type i) const
  {
    if (i < 0 || i >= m_numel)
      err_index_out_of_range (2, 2, i+1, m_numel, dims ());

    if (i == 0)
      // Required for proper NaN handling.
      return (m_numel == 1 ? final_value () : m_base);
    else if (i < m_numel - 1)
      return (m_reverse ? m_base + T (i) * m_increment
                        : m_base + T (i) * m_increment);
    else
      return final_value ();
  }

  T checkelem (octave_idx_type i, octave_idx_type j) const
  {
    // Ranges are *always* row vectors.
    if (i != 0)
      err_index_out_of_range (1, 1, i+1, m_numel, dims ());

    return checkelem (j);
  }

  T elem (octave_idx_type i) const
  {
    if (i == 0)
      // Required for proper NaN handling.
      return (m_numel == 1 ? final_value () : m_base);
    else if (i < m_numel - 1)
      return (m_reverse ? m_base - T (i) * m_increment
                        : m_base + T (i) * m_increment);
    else
      return final_value ();
  }

  T elem (octave_idx_type /* i */, octave_idx_type j) const
  {
    return elem (j);
  }

  T operator () (octave_idx_type i) const
  {
    return elem (i);
  }

  T operator () (octave_idx_type i, octave_idx_type j) const
  {
    return elem (i, j);
  }

  Array<T> index (const idx_vector& idx) const
  {
    Array<T> retval;

    octave_idx_type n = m_numel;

    if (idx.is_colon ())
      {
        retval = array_value ().reshape (dim_vector (m_numel, 1));
      }
    else
      {
        if (idx.extent (n) != n)
          err_index_out_of_range (1, 1, idx.extent (n), n, dims ());

        dim_vector idx_dims = idx.orig_dimensions ();
        octave_idx_type idx_len = idx.length (n);

        // taken from Array.cc.
        if (n != 1 && idx_dims.isvector ())
          idx_dims = dim_vector (1, idx_len);

        retval.clear (idx_dims);

        // Loop over all values in IDX, executing the lambda
        // expression for each index value.

        T *array = retval.rwdata ();

        idx.loop (n, [this, &array] (octave_idx_type i)
        {
          if (i == 0)
            // Required for proper NaN handling.
            *array++ = (m_numel == 0 ? m_final : m_base);
          else if (i < m_numel - 1)
            *array++ = (m_reverse ? m_base - T (i) * m_increment
                                  : m_base + T (i) * m_increment);
          else
            *array++ = m_final;
        });
      }

    return retval;
  }

  Array<T> diag (octave_idx_type k) const
  {
    return array_value ().diag (k);
  }

  Array<T> array_value () const
  {
    octave_idx_type nel = numel ();

    Array<T> retval (dim_vector (1, nel));

    if (nel == 1)
      // Required for proper NaN handling.
      retval(0) = final_value ();
    else if (nel > 1)
      {
        // The first element must always be *exactly* the base.
        // E.g, -0 would otherwise become +0 in the loop (-0 + 0*increment).
        retval(0) = m_base;

        if (m_reverse)
          for (octave_idx_type i = 1; i < nel - 1; i++)
            retval.xelem (i) = m_base - i * m_increment;
        else
          for (octave_idx_type i = 1; i < nel - 1; i++)
            retval.xelem (i) = m_base + i * m_increment;

        retval.xelem (nel - 1) = final_value ();
      }

    return retval;
  }

private:

  T m_base;
  T m_increment;
  T m_limit;
  T m_final;
  octave_idx_type m_numel;
  bool m_reverse;

  // Setting the number of elements to zero when the increment is zero
  // is intentional and matches the behavior of Matlab's colon
  // operator.

  // These calculations are appropriate for integer ranges.  There are
  // specializations for double and float.

  void init ()
  {
    if (m_reverse)
      {
        m_numel = ((m_increment == T (0)
                    || (m_limit > m_base && m_increment > T (0))
                    || (m_limit < m_base && m_increment < T (0)))
                   ? T (0)
                   : (m_base - m_limit - m_increment) / m_increment);

        m_final = m_base - (m_numel - 1) * m_increment;
      }
    else
      {
        m_numel = ((m_increment == T (0)
                    || (m_limit > m_base && m_increment < T (0))
                    || (m_limit < m_base && m_increment > T (0)))
                   ? T (0)
                   : (m_limit - m_base + m_increment) / m_increment);

        m_final = m_base + (m_numel - 1) * m_increment;
      }
  }
};

// Specializations defined externally.

template <> OCTAVE_API bool range<double>::all_elements_are_ints () const;
template <> OCTAVE_API bool range<float>::all_elements_are_ints () const;

template <> OCTAVE_API void range<double>::init ();
template <> OCTAVE_API void range<float>::init ();

// For now, only define for floating point types.  However, we only
// need range<float> as a temporary local variable in make_float_range
// in ov.cc.

template <> OCTAVE_API bool range<double>::is_storable () const;
template <> OCTAVE_API bool range<float>::is_storable () const;

template <> OCTAVE_API octave_idx_type range<double>::nnz () const;
template <> OCTAVE_API octave_idx_type range<float>::nnz () const;

OCTAVE_END_NAMESPACE(octave)

#endif
