Eigen/src/Core/util/EmulateArray.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_EMULATE_ARRAY_H
#define EIGEN_EMULATE_ARRAY_H

// CUDA doesn't support the STL containers, so we use our own instead.
#if defined(EIGEN_GPUCC) || defined(EIGEN_AVOID_STL_ARRAY)

namespace Eigen {
template <typename T, size_t n>
class array {
 public:
  typedef T value_type;
  typedef T* iterator;
  typedef const T* const_iterator;

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE iterator begin() { return values; }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const_iterator begin() const { return values; }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE iterator end() { return values + n; }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const_iterator end() const { return values + n; }

  typedef std::reverse_iterator<iterator> reverse_iterator;
  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

  EIGEN_STRONG_INLINE reverse_iterator rbegin() { return reverse_iterator(end()); }
  EIGEN_STRONG_INLINE const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }

  EIGEN_STRONG_INLINE reverse_iterator rend() { return reverse_iterator(begin()); }
  EIGEN_STRONG_INLINE const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& operator[](size_t index) {
    eigen_internal_assert(index < size());
    return values[index];
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& operator[](size_t index) const {
    eigen_internal_assert(index < size());
    return values[index];
  }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& at(size_t index) {
    eigen_assert(index < size());
    return values[index];
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& at(size_t index) const {
    eigen_assert(index < size());
    return values[index];
  }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& front() { return values[0]; }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& front() const { return values[0]; }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& back() { return values[n - 1]; }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& back() const { return values[n - 1]; }

  EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE static std::size_t size() { return n; }

  T values[n];

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array() {}
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v) {
    EIGEN_STATIC_ASSERT(n == 1, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2) {
    EIGEN_STATIC_ASSERT(n == 2, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3) {
    EIGEN_STATIC_ASSERT(n == 3, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
    values[2] = v3;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4) {
    EIGEN_STATIC_ASSERT(n == 4, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
    values[2] = v3;
    values[3] = v4;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5) {
    EIGEN_STATIC_ASSERT(n == 5, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
    values[2] = v3;
    values[3] = v4;
    values[4] = v5;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5,
                                              const T& v6) {
    EIGEN_STATIC_ASSERT(n == 6, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
    values[2] = v3;
    values[3] = v4;
    values[4] = v5;
    values[5] = v6;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5,
                                              const T& v6, const T& v7) {
    EIGEN_STATIC_ASSERT(n == 7, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
    values[2] = v3;
    values[3] = v4;
    values[4] = v5;
    values[5] = v6;
    values[6] = v7;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5,
                                              const T& v6, const T& v7, const T& v8) {
    EIGEN_STATIC_ASSERT(n == 8, YOU_MADE_A_PROGRAMMING_MISTAKE)
    values[0] = v1;
    values[1] = v2;
    values[2] = v3;
    values[3] = v4;
    values[4] = v5;
    values[5] = v6;
    values[6] = v7;
    values[7] = v8;
  }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array(std::initializer_list<T> l) {
    eigen_assert(l.size() == n);
    internal::smart_copy(l.begin(), l.end(), values);
  }
};

// Specialize array for zero size
template <typename T>
class array<T, 0> {
 public:
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& operator[](size_t) {
    eigen_assert(false && "Can't index a zero size array");
    return dummy;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& operator[](size_t) const {
    eigen_assert(false && "Can't index a zero size array");
    return dummy;
  }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& front() {
    eigen_assert(false && "Can't index a zero size array");
    return dummy;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& front() const {
    eigen_assert(false && "Can't index a zero size array");
    return dummy;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& back() {
    eigen_assert(false && "Can't index a zero size array");
    return dummy;
  }
  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& back() const {
    eigen_assert(false && "Can't index a zero size array");
    return dummy;
  }

  static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE std::size_t size() { return 0; }

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE array() : dummy() {}

  EIGEN_DEVICE_FUNC array(std::initializer_list<T> l) : dummy() {
    EIGEN_UNUSED_VARIABLE(l);
    eigen_assert(l.size() == 0);
  }

 private:
  T dummy;
};

// Comparison operator
// Todo: implement !=, <, <=, >,  and >=
template <class T, std::size_t N>
EIGEN_DEVICE_FUNC bool operator==(const array<T, N>& lhs, const array<T, N>& rhs) {
  for (std::size_t i = 0; i < N; ++i) {
    if (lhs[i] != rhs[i]) {
      return false;
    }
  }
  return true;
}

namespace internal {
template <std::size_t I_, class T, std::size_t N>
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T& array_get(array<T, N>& a) {
  return a[I_];
}
template <std::size_t I_, class T, std::size_t N>
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T& array_get(const array<T, N>& a) {
  return a[I_];
}

template <class T, std::size_t N>
struct array_size<array<T, N> > {
  static constexpr Index value = N;
};
template <class T, std::size_t N>
struct array_size<array<T, N>&> {
  static constexpr Index value = N;
};
template <class T, std::size_t N>
struct array_size<const array<T, N> > {
  static constexpr Index value = N;
};
template <class T, std::size_t N>
struct array_size<const array<T, N>&> {
  static constexpr Index value = N;
};

}  // end namespace internal
}  // end namespace Eigen

#else

// The compiler supports c++11, and we're not targeting cuda: use std::array as Eigen::array
#include <array>

namespace Eigen {

template <typename T, std::size_t N>
using array = std::array<T, N>;

namespace internal {
/* std::get is only constexpr in C++14, not yet in C++11
 *     - libstdc++ from version 4.7 onwards has it nevertheless,
 *                                          so use that
 *     - libstdc++ older versions: use _M_instance directly
 *     - libc++ all versions so far: use __elems_ directly
 *     - all other libs: use std::get to be portable, but
 *                       this may not be constexpr
 */
#if defined(__GLIBCXX__) && __GLIBCXX__ < 20120322
#define STD_GET_ARR_HACK a._M_instance[I_]
#elif defined(_LIBCPP_VERSION)
#define STD_GET_ARR_HACK a.__elems_[I_]
#else
#define STD_GET_ARR_HACK std::template get<I_, T, N>(a)
#endif

template <std::size_t I_, class T, std::size_t N>
constexpr inline T& array_get(std::array<T, N>& a) {
  return (T&)STD_GET_ARR_HACK;
}
template <std::size_t I_, class T, std::size_t N>
constexpr inline T&& array_get(std::array<T, N>&& a) {
  return (T&&)STD_GET_ARR_HACK;
}
template <std::size_t I_, class T, std::size_t N>
constexpr inline T const& array_get(std::array<T, N> const& a) {
  return (T const&)STD_GET_ARR_HACK;
}

#undef STD_GET_ARR_HACK

}  // end namespace internal
}  // end namespace Eigen

#endif

#endif  // EIGEN_EMULATE_ARRAY_H