+       struct Modifier {
+               enum Position { NONE, PREFIX, POSTFIX };
+               unsigned short ID;
+               const char * const Alias;
+               Position Pos;
+               Version SelectVersion;
+               Modifier (unsigned short const &id, const char * const alias, Position const &pos,
+                         Version const &select) : ID(id), Alias(alias), Pos(pos),
+                        SelectVersion(select) {};
+       };
+
+       static bool FromCommandLine(VersionContainerInterface * const vci, pkgCacheFile &Cache,
+                                   const char **cmdline, Version const &fallback,
+                                   CacheSetHelper &helper);
+
+       static bool FromString(VersionContainerInterface * const vci, pkgCacheFile &Cache,
+                              std::string pkg, Version const &fallback, CacheSetHelper &helper,
+                              bool const onlyFromName = false);
+
+       static bool FromPackage(VersionContainerInterface * const vci, pkgCacheFile &Cache,
+                               pkgCache::PkgIterator const &P, Version const &fallback,
+                               CacheSetHelper &helper);
+
+       static bool FromModifierCommandLine(unsigned short &modID,
+                                           VersionContainerInterface * const vci,
+                                           pkgCacheFile &Cache, const char * cmdline,
+                                           std::list<Modifier> const &mods,
+                                           CacheSetHelper &helper);
+
+protected:                                                             /*{{{*/
+
+       /** \brief returns the candidate version of the package
+
+           \param Cache to be used to query for information
+           \param Pkg we want the candidate version from this package */
+       static pkgCache::VerIterator getCandidateVer(pkgCacheFile &Cache,
+               pkgCache::PkgIterator const &Pkg, CacheSetHelper &helper);
+
+       /** \brief returns the installed version of the package
+
+           \param Cache to be used to query for information
+           \param Pkg we want the installed version from this package */
+       static pkgCache::VerIterator getInstalledVer(pkgCacheFile &Cache,
+               pkgCache::PkgIterator const &Pkg, CacheSetHelper &helper);
+                                                                       /*}}}*/
+};
+                                                                       /*}}}*/
+template<class Container> class VersionContainer : public VersionContainerInterface {/*{{{*/
+/** \class APT::PackageContainer
+
+    Simple wrapper around a container class like std::set to provide a similar
+    interface to a set of versions as to the complete set of all versions in the
+    pkgCache. */
+       Container _cont;
+public:                                                                        /*{{{*/
+       /** \brief smell like a pkgCache::VerIterator */
+       class const_iterator : public VersionContainerInterface::const_iterator,
+                              public std::iterator<std::forward_iterator_tag, typename Container::const_iterator> {/*{{{*/
+               typename Container::const_iterator _iter;
+       public:
+               const_iterator(typename Container::const_iterator i) : _iter(i) {}
+               pkgCache::VerIterator getVer(void) const { return *_iter; }
+               inline pkgCache::VerIterator operator*(void) const { return *_iter; };
+               operator typename Container::const_iterator(void) const { return _iter; }
+               inline void operator++(void) { ++_iter; };
+               inline bool operator!=(const_iterator const &i) const { return _iter != i._iter; };
+               inline bool operator==(const_iterator const &i) const { return _iter == i._iter; };
+               friend std::ostream& operator<<(std::ostream& out, const_iterator i) { return operator<<(out, *i); }
+       };
+       // we are not going to allow modify our veriterators (it doesn't make sense)…
+       typedef APT::VersionContainer<Container>::const_iterator iterator;
+                                                                       /*}}}*/
+
+       bool insert(pkgCache::VerIterator const &V) { if (V.end() == true) return false; _cont.insert(V); return true; };
+       template<class Cont> void insert(VersionContainer<Cont> const &vercont) { _cont.insert((typename Cont::const_iterator)vercont.begin(), (typename Cont::const_iterator)vercont.end()); };
+       void insert(const_iterator begin, const_iterator end) { _cont.insert(begin, end); };
+       bool empty() const { return _cont.empty(); };
+       void clear() { return _cont.clear(); };
+       void erase(iterator position) { _cont.erase((typename Container::const_iterator)position); };
+       size_t erase(const pkgCache::PkgIterator x) { return _cont.erase(x); };
+       void erase(iterator first, iterator last) { _cont.erase(first, last); };
+       size_t size() const { return _cont.size(); };
+
+       const_iterator begin() const { return const_iterator(_cont.begin()); };
+       const_iterator end() const { return const_iterator(_cont.end()); };
+       const_iterator find(pkgCache::VerIterator const &V) const { return const_iterator(_cont.find(V)); };
+