text: //
  // Copyright (c) 2016-2018 João Baptista de Paula e Silva.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in all
  // copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  // SOFTWARE.
  //
  
  
  #pragma once
  
  namespace util
  {
      template <typename T>
      class ContainerEntry final
      {
          T* cont;
          typename T::iterator it;
      public:
          using iterator = typename T::iterator;
  
          ContainerEntry() : cont(nullptr), it() {}
          ContainerEntry(T& cont, typename T::iterator it) : cont(&cont), it(it) {}
          ~ContainerEntry() { if (cont) cont->erase(it); }
  
          ContainerEntry(const ContainerEntry &other) = delete;
          ContainerEntry(ContainerEntry&& other) noexcept : ContainerEntry() { swap(*this, other); }
  
          ContainerEntry &operator=(ContainerEntry other) { swap(*this, other); return *this; }
  
          friend void swap(ContainerEntry &c1, ContainerEntry &c2) noexcept
          {
              using std::swap;
              swap(c1.cont, c2.cont);
              swap(c1.it, c2.it);
          }
      };
  }
  