Optional.h

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//     ____   ______ __
//    / __ \ / ____// /
//   / /_/ // /    / /
//  / ____// /___ / /___   PixInsight Class Library
// /_/     \____//_____/   PCL 2.7.0
// ----------------------------------------------------------------------------
// pcl/Optional.h - Released 2024-06-18T15:48:54Z
// ----------------------------------------------------------------------------
// This file is part of the PixInsight Class Library (PCL).
// PCL is a multiplatform C++ framework for development of PixInsight modules.
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// ----------------------------------------------------------------------------
 
#ifndef __PCL_Optional_h
#define __PCL_Optional_h
 
 
#include <pcl/Defs.h>
#include <pcl/Diagnostics.h>
 
#include <pcl/Exception.h>
 
namespace pcl
{
 
// ----------------------------------------------------------------------------
 
template <class T>
class PCL_CLASS Optional
{
public:
 
   Optional()
      : m_value() // N.B: this initialization prevents warnings such as
   {              // 'Optional<>::m_value may be used uninitialized...'
   }
 
   Optional( const Optional& ) = default;
 
   /*
    * Move constructor.
    */
   Optional( Optional&& ) = default;
 
   Optional( const T& value )
      : m_value( value )
      , m_defined( true )
   {
   }
 
   Optional& operator =( const Optional& x )
   {
      if ( bool( m_defined = x.m_defined ) )
         m_value = x.m_value;
      return *this;
   }
 
   Optional& operator =( Optional&& x )
   {
      if ( bool( m_defined = x.m_defined ) )
         m_value = std::move( x.m_value );
      return *this;
   }
 
   Optional& operator =( const T& value )
   {
      m_value = value;
      m_defined = true;
      return *this;
   }
 
   operator const T&() const
   {
      return m_value;
   }
 
   const T& operator ()() const
   {
      return m_value;
   }
 
   bool IsDefined() const
   {
      return m_defined;
   }
 
   void Undefine()
   {
      m_value = T();
      m_defined = false;
   }
 
   const T& OrElse( const T& value ) const
   {
      return m_defined ? m_value : value;
   }
 
   template <class E>
   const T& OrElseThrow( const Exception& exception ) const
   {
      if ( m_defined )
         return m_value;
      throw exception;
   }
 
   const T& OrElseThrow( const String& message ) const
   {
      if ( m_defined )
         return m_value;
      throw Error( message );
   }
 
   bool operator ==( const Optional& x ) const
   {
      return m_defined ? (x.m_defined ? m_value == x.m_value : false) : !x.m_defined;
   }
 
   bool operator ==( const T& value ) const
   {
      return m_defined && m_value == value;
   }
 
   bool operator <( const Optional& x ) const
   {
      return m_defined && (!x.m_defined || m_value < x.m_value);
   }
 
   bool operator <( const T& value ) const
   {
      return m_defined && m_value < value;
   }
 
private:
 
   T    m_value;
   bool m_defined = false;
};
 
// ----------------------------------------------------------------------------
 
} // pcl
 
#endif   // __PCL_Optional_h
 
// ----------------------------------------------------------------------------
// EOF pcl/Optional.h - Released 2024-06-18T15:48:54Z