rangeutilities.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:
// SPDX-FileCopyrightInfo: Copyright (C) DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
#ifndef DUNE_COMMON_RANGE_UTILITIES_HH
#define DUNE_COMMON_RANGE_UTILITIES_HH
 
#include <dune/common/typetraits.hh>
#include <algorithm>
#include <utility>
#include <type_traits>
#include <bitset>
 
namespace Dune
{
 
  template <typename T,
            typename std::enable_if<IsIterable<T>::value, int>::type = 0>
  typename T::value_type
  max_value(const T & v) {
    using std::max_element;
    return *max_element(v.begin(), v.end());
  }
 
  template <typename T,
            typename std::enable_if<!IsIterable<T>::value, int>::type = 0>
  const T & max_value(const T & v) { return v; }
 
  template <typename T,
            typename std::enable_if<IsIterable<T>::value, int>::type = 0>
  typename T::value_type
  min_value(const T & v) {
    using std::min_element;
    return *min_element(v.begin(), v.end());
  }
 
  template <typename T,
            typename std::enable_if<!IsIterable<T>::value, int>::type = 0>
  const T & min_value(const T & v) { return v; }
 
  template <typename T,
            typename std::enable_if<IsIterable<T>::value, int>::type = 0>
  bool any_true(const T & v) {
    bool b = false;
    for (const auto & e : v)
      b = b or bool(e);
    return b;
  }
 
  template <typename T,
            typename std::enable_if<!IsIterable<T>::value, int>::type = 0>
  bool any_true(const T & v) { return v; }
 
  template<std::size_t N>
  bool any_true(const std::bitset<N> & b)
  {
    return b.any();
  }
 
  template <typename T,
            typename std::enable_if<IsIterable<T>::value, int>::type = 0>
  bool all_true(const T & v) {
    bool b = true;
    for (const auto & e : v)
      b = b and bool(e);
    return b;
  }
 
  template <typename T,
            typename std::enable_if<!IsIterable<T>::value, int>::type = 0>
  bool all_true(const T & v) { return v; }
 
  template<std::size_t N>
  bool all_true(const std::bitset<N> & b)
  {
    return b.all();
  }
 
 
 
  namespace Impl
  {
 
    template <class T>
    class IntegralRangeIterator
    {
    public:
      typedef std::random_access_iterator_tag iterator_category;
      typedef T value_type;
      typedef std::make_signed_t<T> difference_type;
      typedef const T *pointer;
      typedef T reference;
 
      constexpr IntegralRangeIterator() noexcept : value_(0) {}
      constexpr explicit IntegralRangeIterator(value_type value) noexcept : value_(value) {}
 
      pointer operator->() const noexcept { return &value_; }
      constexpr reference operator*() const noexcept { return value_; }
 
      constexpr reference operator[]( difference_type n ) const noexcept { return (value_ + n); }
 
      constexpr bool operator==(const IntegralRangeIterator & other) const noexcept { return (value_ == other.value_); }
      constexpr bool operator!=(const IntegralRangeIterator & other) const noexcept { return (value_ != other.value_); }
 
      constexpr bool operator<(const IntegralRangeIterator & other) const noexcept { return (value_ <= other.value_); }
      constexpr bool operator<=(const IntegralRangeIterator & other) const noexcept { return (value_ <= other.value_); }
      constexpr bool operator>(const IntegralRangeIterator & other) const noexcept { return (value_ >= other.value_); }
      constexpr bool operator>=(const IntegralRangeIterator & other) const noexcept { return (value_ >= other.value_); }
 
      IntegralRangeIterator& operator++() noexcept { ++value_; return *this; }
      IntegralRangeIterator operator++(int) noexcept { IntegralRangeIterator copy( *this ); ++(*this); return copy; }
 
      IntegralRangeIterator& operator--() noexcept { --value_; return *this; }
      IntegralRangeIterator operator--(int) noexcept { IntegralRangeIterator copy( *this ); --(*this); return copy; }
 
      IntegralRangeIterator& operator+=(difference_type n) noexcept { value_ += n; return *this; }
      IntegralRangeIterator& operator-=(difference_type n) noexcept { value_ -= n; return *this; }
 
      friend constexpr IntegralRangeIterator operator+(const IntegralRangeIterator &a, difference_type n) noexcept { return IntegralRangeIterator(a.value_ + n); }
      friend constexpr IntegralRangeIterator operator+(difference_type n, const IntegralRangeIterator &a) noexcept { return IntegralRangeIterator(a.value_ + n); }
      friend constexpr IntegralRangeIterator operator-(const IntegralRangeIterator &a, difference_type n) noexcept { return IntegralRangeIterator(a.value_ - n); }
 
      constexpr difference_type operator-(const IntegralRangeIterator &other) const noexcept { return (static_cast<difference_type>(value_) - static_cast<difference_type>(other.value_)); }
 
    private:
      value_type value_;
    };
 
  } // namespace Impl
 
 
 
  template <class T>
  class IntegralRange
  {
  public:
    typedef T value_type;
    typedef Impl::IntegralRangeIterator<T> iterator;
    typedef std::make_unsigned_t<T> size_type;
 
    constexpr IntegralRange(value_type from, value_type to) noexcept : from_(from), to_(to) {}
    constexpr explicit IntegralRange(value_type to) noexcept : from_(0), to_(to) {}
    constexpr IntegralRange(std::pair<value_type, value_type> range) noexcept : from_(range.first), to_(range.second) {}
 
    constexpr iterator begin() const noexcept { return iterator(from_); }
    constexpr iterator end() const noexcept { return iterator(to_); }
 
    constexpr value_type operator[](const value_type &i) const noexcept { return (from_ + i); }
 
    constexpr bool empty() const noexcept { return (from_ == to_); }
    constexpr size_type size() const noexcept { return (static_cast<size_type>(to_) - static_cast<size_type>(from_)); }
 
  private:
    value_type from_, to_;
  };
 
 
  template <class T, T to, T from = 0>
  class StaticIntegralRange
  {
    template <T ofs, T... i>
    static std::integer_sequence<T, (i+ofs)...> shift_integer_sequence(std::integer_sequence<T, i...>);
 
  public:
    typedef T value_type;
    typedef Impl::IntegralRangeIterator<T> iterator;
    typedef std::make_unsigned_t<T> size_type;
 
    typedef decltype(shift_integer_sequence<from>(std::make_integer_sequence<T, to-from>())) integer_sequence;
 
    constexpr StaticIntegralRange() noexcept = default;
 
    constexpr operator IntegralRange<T>() const noexcept { return {from, to}; }
    constexpr operator integer_sequence() const noexcept { return {}; }
 
    static constexpr iterator begin() noexcept { return iterator(from); }
    static constexpr iterator end() noexcept { return iterator(to); }
 
    template <class U, U i>
    constexpr auto operator[](const std::integral_constant<U, i> &) const noexcept
      -> std::integral_constant<value_type, from + static_cast<value_type>(i)>
    {
      return {};
    }
 
    constexpr value_type operator[](const size_type &i) const noexcept { return (from + static_cast<value_type>(i)); }
 
    static constexpr std::integral_constant<bool, from == to> empty() noexcept { return {}; }
    static constexpr std::integral_constant<size_type, static_cast<size_type>(to) - static_cast<size_type>(from) > size() noexcept { return {}; }
  };
 
  template<class T, class U,
           std::enable_if_t<std::is_same<std::decay_t<T>, std::decay_t<U>>::value, int> = 0,
           std::enable_if_t<std::is_integral<std::decay_t<T>>::value, int> = 0>
  inline static IntegralRange<std::decay_t<T>> range(T &&from, U &&to) noexcept
  {
    return IntegralRange<std::decay_t<T>>(std::forward<T>(from), std::forward<U>(to));
  }
 
  template<class T, std::enable_if_t<std::is_integral<std::decay_t<T>>::value, int> = 0>
  inline static IntegralRange<std::decay_t<T>> range(T &&to) noexcept
  {
    return IntegralRange<std::decay_t<T>>(std::forward<T>(to));
  }
 
  template<class T, std::enable_if_t<std::is_enum<std::decay_t<T>>::value, int> = 0>
  inline static IntegralRange<std::underlying_type_t<std::decay_t<T>>> range(T &&to) noexcept
  {
    return IntegralRange<std::underlying_type_t<std::decay_t<T>>>(std::forward<T>(to));
  }
 
  template<class T, T from, T to>
  inline static StaticIntegralRange<T, to, from> range(std::integral_constant<T, from>, std::integral_constant<T, to>) noexcept
  {
    return {};
  }
 
  template<class T, T to>
  inline static StaticIntegralRange<T, to> range(std::integral_constant<T, to>) noexcept
  {
    return {};
  }
 
 
 
  struct ValueTransformationTag {};
 
  struct IteratorTransformationTag {};
 
  namespace Impl
  {
 
    // Helper class to mimic a pointer for proxy objects.
    // This is needed to implement operator-> on an iterator
    // using proxy-values. It stores the proxy value but
    // provides operator-> like a pointer.
    template<class ProxyType>
    class PointerProxy
    {
    public:
      PointerProxy(ProxyType&& p) : p_(p)
      {}
 
      ProxyType* operator->()
      {
        return &p_;
      }
 
      ProxyType p_;
    };
 
    // An iterator transforming a wrapped iterator using
    // an unary function. It inherits the iterator-category
    // of the underlying iterator.
    template <class I, class F, class TransformationType, class C = typename std::iterator_traits<I>::iterator_category>
    class TransformedRangeIterator;
 
    template <class I, class F, class TransformationType>
    class TransformedRangeIterator<I,F,TransformationType,std::forward_iterator_tag>
    {
    protected:
 
      static decltype(auto) transform(const F& f, const I& it) {
        if constexpr (std::is_same_v<TransformationType,IteratorTransformationTag>)
          return f(it);
        else
          return f(*it);
      }
 
    public:
      using iterator_category = std::forward_iterator_tag;
      using reference = decltype(transform(std::declval<F>(), std::declval<I>()));
      using value_type = std::decay_t<reference>;
      using pointer = PointerProxy<value_type>;
 
      // If we later want to allow standalone TransformedRangeIterators,
      // we could customize the FunctionPointer to be a default-constructible,
      // copy-assignable type storing a function but acting like a pointer
      // to function.
      using FunctionPointer = const F*;
 
      constexpr TransformedRangeIterator(const I& it, FunctionPointer f) noexcept :
        it_(it),
        f_(f)
      {}
 
      // Explicitly initialize members. Using a plain
      //
      //   constexpr TransformedRangeIterator() noexcept {}
      //
      // would default-initialize the members while
      //
      //   constexpr TransformedRangeIterator() noexcept : it_(), f_() {}
      //
      // leads to value-initialization. This is a case where
      // both are really different. If it_ is a raw pointer (i.e. POD)
      // then default-initialization leaves it uninitialized while
      // value-initialization zero-initializes it.
      constexpr TransformedRangeIterator() noexcept :
        it_(),
        f_()
      {}
 
      // Dereferencing returns a value created by the function
      constexpr reference operator*() const noexcept {
        return transform(*f_, it_);
      }
 
      // Dereferencing returns a value created by the function
      pointer operator->() const noexcept {
        return transform(*f_, it_);
      }
 
      constexpr TransformedRangeIterator& operator=(const TransformedRangeIterator& other) = default;
 
      constexpr bool operator==(const TransformedRangeIterator& other) const noexcept {
        return (it_ == other.it_);
      }
 
      constexpr bool operator!=(const TransformedRangeIterator& other) const noexcept {
        return (it_ != other.it_);
      }
 
      TransformedRangeIterator& operator++() noexcept {
        ++it_;
        return *this;
      }
 
      TransformedRangeIterator operator++(int) noexcept {
        TransformedRangeIterator copy(*this);
        ++(*this);
        return copy;
      }
 
    protected:
      I it_;
      FunctionPointer f_;
    };
 
 
 
    template <class I, class F, class T>
    class TransformedRangeIterator<I,F,T,std::bidirectional_iterator_tag> :
      public TransformedRangeIterator<I,F,T,std::forward_iterator_tag>
    {
    protected:
      using Base = TransformedRangeIterator<I,F,T,std::forward_iterator_tag>;
      using Base::it_;
      using Base::f_;
    public:
      using iterator_category = std::bidirectional_iterator_tag;
      using reference = typename Base::reference;
      using value_type = typename Base::value_type;
      using pointer = typename Base::pointer;
 
      using FunctionPointer = typename Base::FunctionPointer;
 
      using Base::Base;
 
      // Member functions of the forward_iterator that need
      // to be redefined because the base class methods return a
      // forward_iterator.
      constexpr TransformedRangeIterator& operator=(const TransformedRangeIterator& other) = default;
 
      TransformedRangeIterator& operator++() noexcept {
        ++it_;
        return *this;
      }
 
      TransformedRangeIterator operator++(int) noexcept {
        TransformedRangeIterator copy(*this);
        ++(*this);
        return copy;
      }
 
      // Additional member functions of bidirectional_iterator
      TransformedRangeIterator& operator--() noexcept {
        --(this->it_);
        return *this;
      }
 
      TransformedRangeIterator operator--(int) noexcept {
        TransformedRangeIterator copy(*this);
        --(*this);
        return copy;
      }
    };
 
 
 
    template <class I, class F, class T>
    class TransformedRangeIterator<I,F,T,std::random_access_iterator_tag> :
      public TransformedRangeIterator<I,F,T,std::bidirectional_iterator_tag>
    {
    protected:
      using Base = TransformedRangeIterator<I,F,T,std::bidirectional_iterator_tag>;
      using Base::it_;
      using Base::f_;
    public:
      using iterator_category = std::random_access_iterator_tag;
      using reference = typename Base::reference;
      using value_type = typename Base::value_type;
      using pointer = typename Base::pointer;
      using difference_type = typename std::iterator_traits<I>::difference_type;
 
      using FunctionPointer = typename Base::FunctionPointer;
 
      using Base::Base;
 
      // Member functions of the forward_iterator that need
      // to be redefined because the base class methods return a
      // forward_iterator.
      constexpr TransformedRangeIterator& operator=(const TransformedRangeIterator& other) = default;
 
      TransformedRangeIterator& operator++() noexcept {
        ++it_;
        return *this;
      }
 
      TransformedRangeIterator operator++(int) noexcept {
        TransformedRangeIterator copy(*this);
        ++(*this);
        return copy;
      }
 
      // Member functions of the bidirectional_iterator that need
      // to be redefined because the base class methods return a
      // bidirectional_iterator.
      TransformedRangeIterator& operator--() noexcept {
        --(this->it_);
        return *this;
      }
 
      TransformedRangeIterator operator--(int) noexcept {
        TransformedRangeIterator copy(*this);
        --(*this);
        return copy;
      }
 
      // Additional member functions of random_access_iterator
      TransformedRangeIterator& operator+=(difference_type n) noexcept {
        it_ += n;
        return *this;
      }
 
      TransformedRangeIterator& operator-=(difference_type n) noexcept {
        it_ -= n;
        return *this;
      }
 
      bool operator<(const TransformedRangeIterator& other) noexcept {
        return it_<other.it_;
      }
 
      bool operator<=(const TransformedRangeIterator& other) noexcept {
        return it_<=other.it_;
      }
 
      bool operator>(const TransformedRangeIterator& other) noexcept {
        return it_>other.it_;
      }
 
      bool operator>=(const TransformedRangeIterator& other) noexcept {
        return it_>=other.it_;
      }
 
      reference operator[](difference_type n) noexcept {
        return Base::transform(*f_, it_+n);
      }
 
      friend
      TransformedRangeIterator operator+(const TransformedRangeIterator& it, difference_type n) noexcept {
        return TransformedRangeIterator(it.it_+n, it.f_);
      }
 
      friend
      TransformedRangeIterator operator+(difference_type n, const TransformedRangeIterator& it) noexcept {
        return TransformedRangeIterator(n+it.it_, it.f_);
      }
 
      friend
      TransformedRangeIterator operator-(const TransformedRangeIterator& it, difference_type n) noexcept {
        return TransformedRangeIterator(it.it_-n, it.f_);
      }
 
      friend
      difference_type operator-(const TransformedRangeIterator& first, const TransformedRangeIterator& second) noexcept {
        return first.it_-second.it_;
      }
    };
 
 
  } // namespace Impl
 
 
 
  template <class R, class F, class T=ValueTransformationTag>
  class TransformedRangeView
  {
    using  RawConstIterator = std::decay_t<decltype(std::declval<const R>().begin())>;
    using  RawIterator = std::decay_t<decltype(std::declval<R>().begin())>;
 
  public:
 
    using const_iterator = Impl::TransformedRangeIterator<RawConstIterator, F, T>;
 
    using iterator = Impl::TransformedRangeIterator<RawIterator, F, T>;
 
    using RawRange = std::remove_reference_t<R>;
 
    template<class RR>
    constexpr TransformedRangeView(RR&& rawRange, const F& f) noexcept :
      rawRange_(std::forward<RR>(rawRange)),
      f_(f)
    {
      static_assert(std::is_same_v<T, ValueTransformationTag> or std::is_same_v<T, IteratorTransformationTag>,
          "The TransformationType passed to TransformedRangeView has to be either ValueTransformationTag or IteratorTransformationTag.");
    }
 
    constexpr const_iterator begin() const noexcept {
      return const_iterator(rawRange_.begin(), &f_);
    }
 
    constexpr iterator begin() noexcept {
      return iterator(rawRange_.begin(), &f_);
    }
 
    constexpr const_iterator end() const noexcept {
      return const_iterator(rawRange_.end(), &f_);
    }
 
    constexpr iterator end() noexcept {
      return iterator(rawRange_.end(), &f_);
    }
 
    template<class Dummy=R,
      class = std::void_t<decltype(std::declval<Dummy>().size())>>
    auto size() const
    {
      return rawRange_.size();
    }
 
    const RawRange& rawRange() const
    {
      return rawRange_;
    }
 
    RawRange& rawRange()
    {
      return rawRange_;
    }
 
  private:
    R rawRange_;
    F f_;
  };
 
  template <class R, class F>
  auto transformedRangeView(R&& range, const F& f)
  {
    return TransformedRangeView<R, F, ValueTransformationTag>(std::forward<R>(range), f);
  }
 
  template <class R, class F>
  auto iteratorTransformedRangeView(R&& range, const F& f)
  {
    return TransformedRangeView<R, F, IteratorTransformationTag>(std::forward<R>(range), f);
  }
 
 
  template<class Range>
  auto sparseRange(Range&& range) {
    return Dune::iteratorTransformedRangeView(std::forward<Range>(range), [](auto&& it) {
        return std::tuple<decltype(*it), decltype(it.index())>(*it, it.index());
    });
  }
 
}
 
#endif // DUNE_COMMON_RANGE_UTILITIES_HH