scalarvectorview.hh

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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_COMMON_SCALARVECTORVIEW_HH
#define DUNE_COMMON_SCALARVECTORVIEW_HH
 
#include <cstddef>
#include <type_traits>
#include <istream>
 
#include <dune/common/densevector.hh>
#include <dune/common/fvector.hh>
#include <dune/common/typetraits.hh>
#include <dune/common/matvectraits.hh>
 
namespace Dune {
 
namespace Impl {
 
  template<class K>
  class ScalarVectorView :
    public DenseVector<ScalarVectorView<K>>
  {
    K* dataP_;
    using Base = DenseVector<ScalarVectorView<K>>;
 
    template <class>
    friend class ScalarVectorView;
  public:
 
    enum {
      dimension = 1
    };
 
    using size_type = typename Base::size_type;
 
    using reference = std::decay_t<K>&;
 
    using const_reference = const K&;
 
    //===== construction
 
    constexpr ScalarVectorView ()
      : dataP_(nullptr)
    {}
 
    ScalarVectorView (K* p) :
      dataP_(p)
    {}
 
    ScalarVectorView (const ScalarVectorView &other) :
      Base(),
      dataP_(other.dataP_)
    {}
 
    ScalarVectorView (ScalarVectorView &&other) :
      Base(),
      dataP_( other.dataP_ )
    {}
 
    ScalarVectorView& operator= (const ScalarVectorView& other)
    {
      assert(dataP_);
      assert(other.dataP_);
      *dataP_ = *(other.dataP_);
      return *this;
    }
 
    template<class KK>
    ScalarVectorView& operator= (const ScalarVectorView<KK>& other)
    {
      assert(dataP_);
      assert(other.dataP_);
      *dataP_ = *(other.dataP_);
      return *this;
    }
 
    template<typename T,
      std::enable_if_t<std::is_convertible<T, K>::value, int> = 0>
    inline ScalarVectorView& operator= (const T& k)
    {
      *dataP_ = k;
      return *this;
    }
 
    static constexpr size_type size ()
    {
      return 1;
    }
 
    K& operator[] ([[maybe_unused]] size_type i)
    {
      DUNE_ASSERT_BOUNDS(i == 0);
      return *dataP_;
    }
 
    const K& operator[] ([[maybe_unused]] size_type i) const
    {
      DUNE_ASSERT_BOUNDS(i == 0);
      return *dataP_;
    }
  }; // class ScalarVectorView
 
} // namespace Impl
 
 
  template< class K>
  struct DenseMatVecTraits< Impl::ScalarVectorView<K> >
  {
    using derived_type = Impl::ScalarVectorView<K>;
    using value_type = std::remove_const_t<K>;
    using size_type = std::size_t;
  };
 
  template< class K >
  struct FieldTraits< Impl::ScalarVectorView<K> > : public FieldTraits<std::remove_const_t<K>> {};
 
  template<class K>
  struct AutonomousValueType<Impl::ScalarVectorView<K>>
  {
    using type = FieldVector<std::remove_const_t<K>,1>;
  };
 
namespace Impl {
 
  template<class K>
  inline std::istream &operator>> ( std::istream &in, ScalarVectorView<K> &v )
  {
    K w;
    if(in >> w)
      v = w;
    return in;
  }
 
 
  template<class T,
    std::enable_if_t<IsNumber<T>::value, int> = 0>
  auto asVector(T& t)
  {
    return ScalarVectorView<T>{&t};
  }
 
  template<class T,
    std::enable_if_t<IsNumber<T>::value, int> = 0>
  auto asVector(const T& t)
  {
    return ScalarVectorView<const T>{&t};
  }
 
  template<class T,
    std::enable_if_t<not IsNumber<T>::value, int> = 0>
  T& asVector(T& t)
  {
    return t;
  }
 
  template<class T,
    std::enable_if_t<not IsNumber<T>::value, int> = 0>
  const T& asVector(const T& t)
  {
    return t;
  }
 
} // end namespace Impl
 
} // end namespace Dune
 
#endif // DUNE_COMMON_SCALARVECTORVIEW_HH