Teuchos_Describable.hpp

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00003 // 
00004 //                    Teuchos: Common Tools Package
00005 //                 Copyright (2004) Sandia Corporation
00006 // 
00007 // Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
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00010 // This library is free software; you can redistribute it and/or modify
00011 // it under the terms of the GNU Lesser General Public License as
00012 // published by the Free Software Foundation; either version 2.1 of the
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00015 // This library is distributed in the hope that it will be useful, but
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00018 // Lesser General Public License for more details.
00019 //  
00020 // You should have received a copy of the GNU Lesser General Public
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00023 // Questions? Contact Michael A. Heroux (maherou@sandia.gov) 
00024 // 
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00027 
00028 #ifndef TEUCHOS_DESCRIBABLE_HPP
00029 #define TEUCHOS_DESCRIBABLE_HPP
00030 
00031 #include "Teuchos_VerbosityLevel.hpp"
00032 #include "Teuchos_FancyOStream.hpp"
00033 #include "Teuchos_LabeledObject.hpp"
00034 
00035 
00036 namespace Teuchos {
00037 
00038 
00067 class Describable : virtual public LabeledObject {
00068 public:
00069 
00071   static const EVerbosityLevel   verbLevel_default;
00072 
00074 
00075 
00086   virtual std::string description() const;
00087 
00123   virtual void describe(
00124     FancyOStream &out,
00125     const EVerbosityLevel verbLevel = verbLevel_default
00126     ) const;
00127   
00128 };
00129 
00130 
00131 // Describable stream manipulator state class
00132 //
00133 // This is not a class that a user needs to see and that is why it is not
00134 // being given doxygen documentation!
00135 struct DescribableStreamManipulatorState {
00136   const Describable &describable;
00137   const EVerbosityLevel verbLevel;
00138   DescribableStreamManipulatorState(
00139     const Describable &_describable,
00140     const EVerbosityLevel _verbLevel = VERB_MEDIUM
00141     )
00142     :describable(_describable)
00143     ,verbLevel(_verbLevel)
00144     {}
00145 };
00146 
00147 
00169 inline DescribableStreamManipulatorState describe(
00170   const Describable &describable,
00171   const EVerbosityLevel verbLevel = Describable::verbLevel_default
00172   )
00173 {
00174   return DescribableStreamManipulatorState(describable,verbLevel);
00175 }
00176 
00177 
00204 inline
00205 std::ostream& operator<<(
00206   std::ostream& os, const DescribableStreamManipulatorState& d
00207   )
00208 {
00209   d.describable.describe(*getFancyOStream(Teuchos::rcp(&os,false)),d.verbLevel);
00210   return os;
00211 }
00212 
00213 //
00214 // RAB: Note: The above function works with an std::ostream object even
00215 // through Describable::describe(...) requires a FancyOStream object.  We must
00216 // write the stream manipulator in terms of std::ostream, or compound output
00217 // statements like:
00218 //
00219 //  void foo( FancyOStream &out, Describable &d, EVerbLevel verbLevel )
00220 //    {
00221 //      out << "\nThis is the describable object d:" << describe(d,verbLevel);
00222 //    }
00223 //
00224 // will not work correctly.  The problem is that the first output
00225 //
00226 //   out << "\nThis is the describable object d:"
00227 //
00228 //  must return a reference to an std::ostream object.  This should mean that
00229 //  the next statement, which is basically:
00230 //
00231 //    static_cast<std::ostream&>(out) << DescribableStreamManipulatorState
00232 //
00233 // should not even compile.  However, under gcc 3.4.3, the code did compile
00234 // but did not call the above function.  Instead, it set up some type of
00235 // infinite recursion that resulted in a segfault due to the presence of the
00236 // Teuchos::any class!
00237 //
00238 
00239 
00240 } // namespace Teuchos
00241 
00242 #endif // TEUCHOS_DESCRIBABLE_HPP

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