range.h

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/*******************************************************************\
 
Module: Range
 
Author: Romain Brenguier, romain.brenguier@diffblue.com
 
\*******************************************************************/
 
 
#ifndef CPROVER_UTIL_RANGE_H
#define CPROVER_UTIL_RANGE_H
 
#include <util/invariant.h>
 
#include <functional>
#include <memory>
#include <type_traits>
 
template <typename iteratort, typename outputt>
class map_iteratort
{
public:
  using difference_type = typename iteratort::difference_type;
  using value_type = outputt;
  using pointer = const outputt *;
  using reference = const outputt &;
  using iterator_category = std::forward_iterator_tag;
 
  bool operator==(const map_iteratort &other) const
  {
    return underlying == other.underlying;
  }
 
  bool operator!=(const map_iteratort &other) const
  {
    return !(this->underlying == other.underlying);
  }
 
  map_iteratort &operator++()
  {
    PRECONDITION(underlying != underlying_end);
    ++underlying;
    if(underlying != underlying_end)
      current = std::make_shared<outputt>((*f)(*underlying));
    return *this;
  }
 
  map_iteratort operator++(int)
  {
    map_iteratort tmp(*this);
    this->operator++();
    return tmp;
  }
 
  value_type &operator*()
  {
    return *current.get();
  }
 
  value_type *operator->()
  {
    return &(*current.get());
  }
 
  const value_type &operator*() const
  {
    return *current.get();
  }
 
  const value_type *operator->() const
  {
    return &(*current.get());
  }
 
  explicit map_iteratort(
    iteratort underlying,
    iteratort underlying_end,
    std::shared_ptr<
      std::function<value_type(const typename iteratort::value_type &)>> f)
    : underlying(std::move(underlying)),
      underlying_end(std::move(underlying_end)),
      f(std::move(f))
  {
    if(this->underlying != this->underlying_end)
      current = std::make_shared<outputt>((*this->f)(*this->underlying));
  }
 
private:
  iteratort underlying;
  iteratort underlying_end;
  std::shared_ptr<
    std::function<value_type(const typename iteratort::value_type &)>>
    f;
 
  std::shared_ptr<outputt> current = nullptr;
};
 
template <typename iteratort>
class filter_iteratort
{
public:
  using difference_type = typename iteratort::difference_type;
  using value_type = typename iteratort::value_type;
  using pointer = typename iteratort::pointer;
  using reference = typename iteratort::reference;
  using iterator_category = std::forward_iterator_tag;
 
  bool operator==(const filter_iteratort &other) const
  {
    return underlying == other.underlying;
  }
 
  bool operator!=(const filter_iteratort &other) const
  {
    return !(this->underlying == other.underlying);
  }
 
  filter_iteratort &operator++()
  {
    ++underlying;
    point_to_first_to_peek();
    return *this;
  }
 
  filter_iteratort operator++(int)
  {
    filter_iteratort tmp(*this);
    this->operator++();
    return tmp;
  }
 
  reference operator*() const
  {
    return *underlying;
  }
 
  pointer operator->() const
  {
    return &(*underlying);
  }
 
  filter_iteratort(
    std::shared_ptr<std::function<bool(const value_type &)>> f,
    iteratort underlying,
    iteratort end)
    : underlying(std::move(underlying)),
      underlying_end(std::move(end)),
      f(std::move(f))
  {
    point_to_first_to_peek();
  }
 
private:
  iteratort underlying;
  const iteratort underlying_end;
  std::shared_ptr<std::function<bool(const value_type &)>> f;
 
  void point_to_first_to_peek()
  {
    while(underlying != underlying_end && !(*f)(*underlying))
      ++underlying;
  }
};
 
template <typename first_iteratort, typename second_iteratort>
struct concat_iteratort
{
public:
  using difference_type = typename first_iteratort::difference_type;
  using value_type = typename first_iteratort::value_type;
  using pointer = typename first_iteratort::pointer;
  using reference = typename first_iteratort::reference;
  using iterator_category = std::forward_iterator_tag;
 
  static_assert(
    std::is_same<value_type, typename first_iteratort::value_type>::value,
    "Concatenated iterators should have the same value type");
 
  bool operator==(const concat_iteratort &other) const
  {
    return first_begin == other.first_begin && first_end == other.first_end &&
           second_begin == other.second_begin;
  }
 
  bool operator!=(const concat_iteratort &other) const
  {
    return !(*this == other);
  }
 
  concat_iteratort &operator++()
  {
    if(first_begin == first_end)
      ++second_begin;
    else
      ++first_begin;
    return *this;
  }
 
  concat_iteratort operator++(int)
  {
    concat_iteratort tmp(first_begin, first_end, second_begin);
    this->operator++();
    return tmp;
  }
 
  reference operator*() const
  {
    if(first_begin == first_end)
      return *second_begin;
    return *first_begin;
  }
 
  pointer operator->() const
  {
    if(first_begin == first_end)
      return &(*second_begin);
    return &(*first_begin);
  }
 
  concat_iteratort(
    first_iteratort first_begin,
    first_iteratort first_end,
    second_iteratort second_begin)
    : first_begin(std::move(first_begin)),
      first_end(std::move(first_end)),
      second_begin(std::move(second_begin))
  {
  }
 
private:
  first_iteratort first_begin;
  first_iteratort first_end;
  second_iteratort second_begin;
};
 
template <
  typename first_iteratort,
  typename second_iteratort,
  bool same_size = true>
struct zip_iteratort
{
public:
  using difference_type = typename first_iteratort::difference_type;
  using value_type = std::pair<
    typename first_iteratort::value_type,
    typename second_iteratort::value_type>;
  using pointer = value_type *;
  using reference = value_type &;
  using iterator_category = std::forward_iterator_tag;
 
  bool operator==(const zip_iteratort &other) const
  {
    if(!same_size && end_reached() && other.end_reached())
      return true;
 
    return first_begin == other.first_begin && first_end == other.first_end &&
           second_begin == other.second_begin && second_end == other.second_end;
  }
 
  bool operator!=(const zip_iteratort &other) const
  {
    return !(*this == other);
  }
 
  zip_iteratort &operator++()
  {
    PRECONDITION(!end_reached());
    ++first_begin;
    ++second_begin;
    INVARIANT(
      !same_size ||
        ((first_begin == first_end) == (second_begin == second_end)),
      "Zipped ranges should have the same size");
    current = !end_reached()
                ? std::make_shared<value_type>(*first_begin, *second_begin)
                : nullptr;
    return *this;
  }
 
  zip_iteratort operator++(int)
  {
    zip_iteratort tmp(first_begin, first_end, second_begin, second_end);
    this->operator++();
    return tmp;
  }
 
  reference operator*() const
  {
    PRECONDITION(current != nullptr);
    return *current;
  }
 
  pointer operator->() const
  {
    return current.get();
  }
 
  zip_iteratort(
    first_iteratort _first_begin,
    first_iteratort _first_end,
    second_iteratort _second_begin,
    second_iteratort _second_end)
    : first_begin(std::move(_first_begin)),
      first_end(std::move(_first_end)),
      second_begin(std::move(_second_begin)),
      second_end(std::move(_second_end))
  {
    PRECONDITION(
      !same_size ||
      ((first_begin == first_end) == (second_begin == second_end)));
    if(first_begin != first_end)
      current = std::make_unique<value_type>(*first_begin, *second_begin);
  }
 
private:
  first_iteratort first_begin;
  first_iteratort first_end;
  second_iteratort second_begin;
  second_iteratort second_end;
  std::shared_ptr<value_type> current = nullptr;
 
  bool end_reached() const
  {
    if(same_size)
    {
      INVARIANT(
        (first_begin == first_end) == (second_begin == second_end),
        "Zip ranges should have same size");
      return first_begin == first_end;
    }
    else
      return first_begin == first_end || second_begin == second_end;
  }
};
 
template <typename iteratort>
struct ranget final
{
public:
  using value_type = typename iteratort::value_type;
 
  ranget(iteratort begin, iteratort end)
    : begin_value(std::move(begin)), end_value(std::move(end))
  {
  }
 
  ranget<filter_iteratort<iteratort>>
  filter(std::function<bool(const value_type &)> f)
  {
    auto shared_f = std::make_shared<decltype(f)>(std::move(f));
    filter_iteratort<iteratort> filter_begin(shared_f, begin(), end());
    filter_iteratort<iteratort> filter_end(shared_f, end(), end());
    return ranget<filter_iteratort<iteratort>>(filter_begin, filter_end);
  }
 
  template <typename functiont>
  auto map(functiont &&f)
  {
    using outputt = typename std::invoke_result<functiont, value_type>::type;
    auto shared_f = std::make_shared<
      std::function<outputt(const typename iteratort::value_type &)>>(
      std::forward<functiont>(f));
    auto map_begin =
      map_iteratort<iteratort, outputt>(begin(), end(), shared_f);
    auto map_end = map_iteratort<iteratort, outputt>(end(), end(), shared_f);
    return ranget<map_iteratort<iteratort, outputt>>(
      std::move(map_begin), std::move(map_end));
  }
 
  template <typename other_iteratort>
  ranget<concat_iteratort<iteratort, other_iteratort>>
  concat(ranget<other_iteratort> other)
  {
    auto concat_begin = concat_iteratort<iteratort, other_iteratort>(
      begin(), end(), other.begin());
    auto concat_end =
      concat_iteratort<iteratort, other_iteratort>(end(), end(), other.end());
    return ranget<concat_iteratort<iteratort, other_iteratort>>(
      concat_begin, concat_end);
  }
 
  template <bool same_size = true, typename other_iteratort>
  ranget<zip_iteratort<iteratort, other_iteratort, same_size>>
  zip(ranget<other_iteratort> other)
  {
    auto zip_begin = zip_iteratort<iteratort, other_iteratort, same_size>(
      begin(), end(), other.begin(), other.end());
    auto zip_end = zip_iteratort<iteratort, other_iteratort, same_size>(
      end(), end(), other.end(), other.end());
    return ranget<zip_iteratort<iteratort, other_iteratort, same_size>>(
      zip_begin, zip_end);
  }
 
  template <bool same_size = true, typename containert>
  auto zip(containert &container)
    -> ranget<zip_iteratort<iteratort, decltype(container.begin()), same_size>>
  {
    return zip<same_size>(
      ranget<decltype(container.begin())>{container.begin(), container.end()});
  }
 
  bool empty() const
  {
    return begin_value == end_value;
  }
 
  ranget<iteratort> drop(std::size_t count) &&
  {
    for(; count > 0 && begin_value != end_value; --count)
      ++begin_value;
    return ranget<iteratort>{std::move(begin_value), std::move(end_value)};
  }
 
  ranget<iteratort> drop(std::size_t count) const &
  {
    return ranget<iteratort>{begin(), end()}.drop(count);
  }
 
  iteratort begin() const
  {
    return begin_value;
  }
 
  const iteratort &end() const
  {
    return end_value;
  }
 
  template <typename containert>
  containert collect() const
  {
    return containert(begin(), end());
  }
 
  template <typename containert>
  operator containert() const
  {
    return collect<containert>();
  }
 
private:
  iteratort begin_value;
  iteratort end_value;
};
 
template <typename iteratort>
ranget<iteratort> make_range(iteratort begin, iteratort end)
{
  return ranget<iteratort>(begin, end);
}
 
template <typename containert>
auto make_range(containert &container) -> ranget<decltype(container.begin())>
{
  return ranget<decltype(container.begin())>(
    container.begin(), container.end());
}
 
template <typename multimapt>
ranget<typename multimapt::const_iterator>
equal_range(const multimapt &multimap, const typename multimapt::key_type &key)
{
  auto iterator_pair = multimap.equal_range(key);
  return make_range(iterator_pair.first, iterator_pair.second);
}
 
#endif // CPROVER_UTIL_RANGE_H