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38b462fd75
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@24546 a592a061-630c-0410-9148-cb99ea01b6c8
80 lines
2.8 KiB
C++
80 lines
2.8 KiB
C++
/**
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* \file foreach.h
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* This file is part of LyX, the document processor.
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* Licence details can be found in the file COPYING.
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*
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* \author Matthias Ettrich
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*
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* Full author contact details are available in file CREDITS.
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*
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*/
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#ifndef FOREACH_H
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#define FOREACH_H
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// Code stolen from Q_FOREACH, augmented to use a reference to the
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// original container instead of a copy. Copies are cheap (if not
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// mutated) for Qt's containers due to copy-on-write. The are less
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// cheap for Standard containers, that's why the modification.
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// Drawback is that we can't use temporary containers as they
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// will be destroyed before the loop is finished. So always write
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//
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// Container const & container = functionReturningTemporaryOrReference()
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// foreach (ContainerItem const & item, container) {
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// ...
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// }
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//
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// to extend the lifetime of the reference.
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#if defined(Q_CC_GNU) && !defined(Q_CC_INTEL)
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/* make use of typeof-extension */
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template <typename T>
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class ForeachContainer {
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public:
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inline ForeachContainer(const T & t) : c(t), brk(0), i(c.begin()), e(c.end()) { }
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const T & c;
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int brk;
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typename T::const_iterator i, e;
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};
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#define foreach(variable, container) \
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for (ForeachContainer<__typeof__(container)> _container_(container); \
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!_container_.brk && _container_.i != _container_.e; \
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__extension__ ({ ++_container_.brk; ++_container_.i; })) \
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for (variable = *_container_.i;; __extension__ ({--_container_.brk; break;}))
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#else
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struct ForeachContainerBase {};
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template <typename T>
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class ForeachContainer : public ForeachContainerBase {
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public:
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inline ForeachContainer(const T& t): c(t), brk(0), i(c.begin()), e(c.end()){};
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const T & c;
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mutable int brk;
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mutable typename T::const_iterator i, e;
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inline bool condition() const { return (!brk++ && i != e); }
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};
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template <typename T> inline T *foreachPointer(const T &) { return 0; }
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template <typename T> inline ForeachContainer<T> foreachContainerNew(const T& t)
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{ return ForeachContainer<T>(t); }
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template <typename T>
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inline const ForeachContainer<T> *foreachContainer(const ForeachContainerBase *base, const T *)
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{ return static_cast<const ForeachContainer<T> *>(base); }
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#define foreach(variable, container) \
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for (const ForeachContainerBase &_container_ = foreachContainerNew(container); \
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foreachContainer(&_container_, true ? 0 : foreachPointer(container))->condition(); \
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++foreachContainer(&_container_, true ? 0 : foreachPointer(container))->i) \
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for (variable = *foreachContainer(&_container_, true ? 0 : foreachPointer(container))->i; \
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foreachContainer(&_container_, true ? 0 : foreachPointer(container))->brk; \
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--foreachContainer(&_container_, true ? 0 : foreachPointer(container))->brk)
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#endif
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#endif // FOREACH_H
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