Teuchos_Describable.hpp

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// @HEADER
// *****************************************************************************
//                    Teuchos: Common Tools Package
//
// Copyright 2004 NTESS and the Teuchos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef TEUCHOS_DESCRIBABLE_HPP
#define TEUCHOS_DESCRIBABLE_HPP

#include "Teuchos_VerbosityLevel.hpp"
#include "Teuchos_FancyOStream.hpp"
#include "Teuchos_LabeledObject.hpp"


namespace Teuchos {


class TEUCHOSCORE_LIB_DLL_EXPORT Describable : virtual public LabeledObject {
public:
  static const EVerbosityLevel verbLevel_default;



  virtual std::string description() const;

  virtual void
  describe (FancyOStream &out,
            const EVerbosityLevel verbLevel = verbLevel_default) const;

  void
  describe (std::ostream &out,
            const EVerbosityLevel verbLevel = verbLevel_default) const;

  virtual ~Describable ();
};


// Describable stream manipulator state class
//
// This is not a class that a user needs to see and that is why it is not
// being given doxygen documentation!
struct DescribableStreamManipulatorState {
  const Describable &describable;
  const EVerbosityLevel verbLevel;
  DescribableStreamManipulatorState(
    const Describable &_describable,
    const EVerbosityLevel _verbLevel = VERB_MEDIUM
    )
    :describable(_describable)
    ,verbLevel(_verbLevel)
    {}
};


inline DescribableStreamManipulatorState describe(
  const Describable &describable,
  const EVerbosityLevel verbLevel = Describable::verbLevel_default
  )
{
  return DescribableStreamManipulatorState(describable,verbLevel);
}


inline
std::ostream& operator<<(
  std::ostream& os, const DescribableStreamManipulatorState& d
  )
{
  d.describable.describe(*getFancyOStream(Teuchos::rcp(&os,false)),d.verbLevel);
  return os;
}

//
// RAB: Note: The above function works with an std::ostream object even
// through Describable::describe(...) requires a FancyOStream object.  We must
// write the stream manipulator in terms of std::ostream, or compound output
// statements like:
//
//  void foo( FancyOStream &out, Describable &d, EVerbLevel verbLevel )
//    {
//      out << "\nThis is the describable object d:" << describe(d,verbLevel);
//    }
//
// will not work correctly.  The problem is that the first output
//
//   out << "\nThis is the describable object d:"
//
//  must return a reference to an std::ostream object.  This should mean that
//  the next statement, which is basically:
//
//    static_cast<std::ostream&>(out) << DescribableStreamManipulatorState
//
// should not even compile.  However, under gcc 3.4.3, the code did compile
// but did not call the above function.  Instead, it set up some type of
// infinite recursion that resulted in a segfault due to the presence of the
// Teuchos::any class!
//


} // namespace Teuchos

#endif // TEUCHOS_DESCRIBABLE_HPP