openmesh/src/OpenMesh/Core/Mesh/SmartRange.hh

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#pragma once

#include <utility>
#include <array>
#include <vector>

//== NAMESPACES ===============================================================

namespace OpenMesh {

//== FORWARD DECLARATION ======================================================

//== CLASS DEFINITION =========================================================

namespace  {

struct Identity
{
  template <typename T>
  T operator()(const T& _t) const { return _t; }
};

}

/// Base class for all smart range types
template <typename RangeT, typename HandleT>
struct SmartRangeT
{
  // TODO: Someone with better c++ knowledge may improve the code below.

  /** @brief Computes the sum of elements.
   *
   * Computes the sum of all elements in the range after applying the functor \p f.
   *
   *  @param f Functor that is applied to all elements before computing the sum
   */
  template <typename Functor>
  auto sum(Functor&& f) -> decltype (f(std::declval<HandleT>())+f(std::declval<HandleT>()))
  {
    auto range = static_cast<const RangeT*>(this);
    auto begin = range->begin();
    auto end   = range->end();
    assert(begin != end);
    decltype (f(*begin) + f(*begin)) sum = f(*begin);
    auto it = begin;
    ++it;
    for (; it != end; ++it)
      sum += f(*it);
    return sum;
  }

  /** @brief Computes the average of elements.
   *
   * Computes the average of all elements in the range after applying the functor \p f.
   *
   *  @param f Functor that is applied to all elements before computing the average.
   */
  template <typename Functor>
  auto avg(Functor&& f) -> decltype (1.0 * (f(std::declval<HandleT>())+f(std::declval<HandleT>())))
  {
    auto range = static_cast<const RangeT*>(this);
    auto begin = range->begin();
    auto end   = range->end();
    assert(begin != end);
    decltype (f(*begin) + f(*begin)) sum = f(*begin);
    auto it = begin;
    ++it;
    int n_elements = 1;
    for (; it != end; ++it)
    {
      sum += f(*it);
      ++n_elements;
    }
    return (1.0 / n_elements) * sum;
  }

  /** @brief Check if any element fulfils condition.
  *
  * Checks if functor \p f returns true for any of the elements in the range.
  * Returns true if that is the case, false otherwise.
  *
  *  @param f Functor that is evaluated for all elements.
  */
  template <typename Functor>
  auto any_of(Functor&& f) -> bool
  {
    auto range = static_cast<const RangeT*>(this);
    for (auto e : *range)
      if (f(e))
        return true;
    return false;
  }

  /** @brief Check if all elements fulfil condition.
  *
  * Checks if functor \p f returns true for all of the elements in the range.
  * Returns true if that is the case, false otherwise.
  *
  *  @param f Functor that is evaluated for all elements.
  */
  template <typename Functor>
  auto all_of(Functor&& f) -> bool
  {
    auto range = static_cast<const RangeT*>(this);
    for (auto e : *range)
      if (!f(e))
        return false;
    return true;
  }

  /** @brief Convert range to array.
  *
  * Converts the range of elements into an array of objects returned by functor \p f.
  * The size of the array needs to be provided by the user. If the size is larger than the number of
  * elements in the range, the remaining entries of the array will be uninitialized.
  *
  *  @param f Functor that is applied to all elements before putting them into the array. If no functor is provided
  *           the array will contain the handles.
  */
  template <int n, typename Functor = Identity>
  auto to_array(Functor&& f = {}) -> std::array<typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type, n>
  {
    auto range = static_cast<const RangeT*>(this);
    std::array<typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type, n> res;
    auto it = range->begin();
    auto end = range->end();
    int i = 0;
    while (i < n && it != end)
      res[i++] = f(*(it++));
    return res;
  }

  /** @brief Convert range to vector.
  *
  * Converts the range of elements into a vector of objects returned by functor \p f.
  *
  *  @param f Functor that is applied to all elements before putting them into the vector. If no functor is provided
  *           the vector will contain the handles.
  */
  template <typename Functor = Identity>
  auto to_vector(Functor&& f = {}) -> std::vector<typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type>
  {
    auto range = static_cast<const RangeT*>(this);
    std::vector<typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type> res;
    for (const auto& e : *range)
      res.push_back(f(e));
    return res;
  }

  /** @brief Compute minimum.
  *
  * Computes the minimum of all objects returned by functor \p f.
  *
  *  @param f Functor that is applied to all elements before computing minimum.
  */
  template <typename Functor>
  auto min(Functor&& f) -> typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type
  {
    using std::min;

    auto range = static_cast<const RangeT*>(this);
    auto it    = range->begin();
    auto end   = range->end();
    assert(it != end);

    typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type res = f(*it);
    ++it;

    for (; it != end; ++it)
      res = min(res, f(*it));

    return res;
  }

  /** @brief Compute maximum.
  *
  * Computes the maximum of all objects returned by functor \p f.
  *
  *  @param f Functor that is applied to all elements before computing maximum.
  */
  template <typename Functor>
  auto max(Functor&& f) -> typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type
  {
    using std::max;

    auto range = static_cast<const RangeT*>(this);
    auto it    = range->begin();
    auto end   = range->end();
    assert(it != end);

    typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type res = f(*it);
    ++it;

    for (; it != end; ++it)
      res = max(res, f(*it));

    return res;
  }

  /** @brief Computes minimum and maximum.
  *
  * Computes the minimum and maximum of all objects returned by functor \p f. Result is returned as std::pair
  * containing minimum as first and maximum as second element.
  *
  *  @param f Functor that is applied to all elements before computing maximum.
  */
  template <typename Functor>
  auto minmax(Functor&& f) -> std::pair<typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type,
                                        typename std::remove_reference<decltype (f(std::declval<HandleT>()))>::type>
  {
    return std::make_pair(this->min(f), this->max(f));
  }





};



//=============================================================================
} // namespace OpenMesh
//=============================================================================

//=============================================================================