ShrinkVectorView.hpp

#ifndef SHRINK_VECTOR_VIEW_HPP
#define SHRINK_VECTOR_VIEW_HPP

#include <utils/PugsAssert.hpp>
#include <utils/PugsMacros.hpp>

#include <cstddef>
#include <iostream>
#include <utils/NaNHelper.hpp>

template <typename VectorType>
class ShrinkVectorView
{
 public:
  using index_type = typename VectorType::index_type;
  using data_type  = typename VectorType::data_type;

 private:
  VectorType& m_vector;
  const size_t m_dimension;

 public:
  friend std::ostream&
  operator<<(std::ostream& os, const ShrinkVectorView& x)
  {
    if (x.size() > 0) {
      os << 0 << ':' << NaNHelper(x[0]);
    }
    for (size_t i = 1; i < x.size(); ++i) {
      os << ' ' << i << ':' << NaNHelper(x[i]);
    }
    return os;
  }

  PUGS_INLINE size_t
  dimension() const noexcept
  {
    return m_dimension;
  }

  PUGS_INLINE
  data_type&
  operator[](index_type i) const noexcept(NO_ASSERT)
  {
    Assert(i < m_dimension, "cannot access element: invalid indices");
    return m_vector[i];
  }

  ShrinkVectorView(VectorType& vector, size_t dimension) noexcept(NO_ASSERT) : m_vector{vector}, m_dimension{dimension}
  {
    Assert(m_dimension <= vector.dimension(), "shrink number of rows must be smaller than original vector's");
  }

  ShrinkVectorView(const ShrinkVectorView&) = delete;
  ShrinkVectorView(ShrinkVectorView&&)      = delete;

  ~ShrinkVectorView() noexcept = default;
};

#endif   // SHRINK_VECTOR_VIEW_HPP