ov-null-mat.h

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////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2008-2025 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
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// Octave is free software: you can redistribute it and/or modify it
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////////////////////////////////////////////////////////////////////////
 
#if ! defined (octave_ov_null_mat_h)
#define octave_ov_null_mat_h 1
 
#include "octave-config.h"
 
#include "ov.h"
#include "ov-re-mat.h"
#include "ov-str-mat.h"
 
// Design rationale:
// The constructors are hidden.  There is only one null matrix (or null string)
// object, that can have shallow copies.  Cloning the object returns just a
// normal empty matrix, so all the shallow copies are, in fact, read-only.
// This conveniently ensures that any attempt to fiddle with the null matrix
// destroys its special status.
 
// The special [] value.
 
class OCTINTERP_API octave_null_matrix : public octave_matrix
{
  octave_null_matrix () : octave_matrix () { }
 
public:
 
  static const octave_value instance;
 
  bool isnull () const { return true; }
  bool vm_need_storable_call () const { return true; }
 
  type_conv_info numeric_conversion_function () const;
 
private:
 
  DECLARE_OV_TYPEID_FUNCTIONS_AND_DATA_API (OCTINTERP_API)
};
 
// The special "" value
 
class OCTINTERP_API octave_null_str : public octave_char_matrix_str
{
  octave_null_str () : octave_char_matrix_str () { }
 
public:
 
  static const octave_value instance;
 
  bool is_storable () const { return false; }
 
  bool isnull () const { return true; }
  bool vm_need_storable_call () const { return true; }
 
  type_conv_info numeric_conversion_function () const;
 
private:
 
  DECLARE_OV_TYPEID_FUNCTIONS_AND_DATA_API (OCTINTERP_API)
};
 
// The special '' value
 
class OCTINTERP_API octave_null_sq_str : public octave_char_matrix_sq_str
{
  octave_null_sq_str () : octave_char_matrix_sq_str () { }
 
public:
 
  static const octave_value instance;
 
  bool is_storable () const { return false; }
 
  bool isnull () const { return true; }
 
  bool vm_need_storable_call () const { return true; }
 
  type_conv_info numeric_conversion_function () const;
 
private:
 
  DECLARE_OV_TYPEID_FUNCTIONS_AND_DATA_API (OCTINTERP_API)
};
 
#endif