JConversion.hh

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#ifndef __JLANG__JCONVERSION__
#define __JLANG__JCONVERSION__
 
#include "JLang/JAssert.hh"
#include "JLang/JTest.hh"
 
/**
 * \author mdejong
 */
 
namespace JLANG {}
namespace JPP { using namespace JLANG; }
 
namespace JLANG {
 
 
  /**
   * Template class test for polymorphism.
   */
  template<class JDerived_t, class JBase_t>
  class JConversion
  {
    /**
     * Test convertibility of two classes.
     *
     * Source code is taken from reference:
     * A. Alexandrescu, Modern C++ Design, Addison Wesley.
     */
    template<class derived_type, class base_type>
    class JLocal  :
      public JTest
    {
      using JTest::test;
      
      static JTrue test(const base_type&);
      
      static derived_type getReference();
      
    public:
      static const bool is_derived = JTEST(test(getReference()));
      static const bool is_same    = false;
    };
    
  public:
    
    static const bool is_derived = JLocal<const JDerived_t*, const JBase_t*>::is_derived;   //!< true, if JDerived_t derives from JBase_t
    static const bool is_same    = JLocal<const JDerived_t*, const JBase_t*>::is_same;      //!< true, if JDerived_t is equal to  JBase_t
  };
  
 
  /**
   * Specialisation of JConversion for identical types.
   */
  template<class T>
  struct JConversion<T,T>
  {
    static const bool is_derived = true;
    static const bool is_same    = true;
  };
 
 
  /**
   * Auxialiary class to assert type conversion.
   */
  template<class JDerived_t, class JBase_t, bool is_derived = JConversion<JDerived_t,JBase_t>::is_derived>
  class JAssertConversion;
 
  /**
   * Implementation of a valid type conversion.
   */
  template<class JDerived_t, class JBase_t>
  class JAssertConversion<JDerived_t, JBase_t, true> {};
}
 
#endif