Ichthyostega
2bd931b6da
The former implementation was more closely based on Loki's Acyclic Visitor. Swapped in the working new concept and adapted the policies and tests. Doesn't compile yet
100 lines
2.8 KiB
C++
100 lines
2.8 KiB
C++
/*
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VISITOR.hpp - Acyclic Visitor library
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Copyright (C) CinelerraCV
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2007, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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====================================================================
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This code is heavily inspired by
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The Loki Library (loki-lib/trunk/include/loki/Visitor.h)
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Copyright (c) 2001 by Andrei Alexandrescu
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This Loki code accompanies the book:
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Alexandrescu, Andrei. "Modern C++ Design: Generic Programming
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and Design Patterns Applied".
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Copyright (c) 2001. Addison-Wesley. ISBN 0201704315
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*/
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#ifndef CINELERRA_VISITORPOLICIES_H
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#define CINELERRA_VISITORPOLICIES_H
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#include "common/error.hpp"
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namespace cinelerra
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{
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namespace visitor
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{
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/* == several Policies usable in conjunction with cinelerra::visitor::Visitable == */
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/**
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* Policy returning just the default return value in case
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* of encountering an unknown Visitor (typically caused by
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* adding a new class to the visitable hierarchy)
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*/
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template<class TOOL>
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struct UseDefault
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{
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typedef TOOL::ReturnType Ret;
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template<class TAR>
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static Ret onUnknown (TAR&, TOOL&)
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{
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return Ret();
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}
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};
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/**
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* Policy to throw when encountering an unknown visiting tool
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*/
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template<class TOOL>
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struct ThrowException
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{
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typedef TOOL::ReturnType Ret;
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template<class TAR>
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static Ret onUnknown (TAR&, TOOL&)
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{
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throw cinelerra::error::Config("unable to decide what tool operation to call");
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}
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};
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/**
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* Policy invoking an catch-all function for processing
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* an unknown tool / target pair
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* @note using this policy effectively enforces
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* implementing a catch-all function \c treat(TAR&)
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*/
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template<class TOOL>
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struct InvokeCatchAllFunction
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{
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typedef TOOL::ReturnType Ret;
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template<class TAR>
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static Ret onUnknown (TAR& target,TOOL& tool)
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{
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return tool.catchAll (target);
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}
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};
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} // namespace visitor
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} // namespace cinelerra
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#endif
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