libostd/ostd/range.hh

/* Ranges for OctaSTD.
 *
 * This file is part of OctaSTD. See COPYING.md for futher information.
 */

#ifndef OSTD_RANGE_HH
#define OSTD_RANGE_HH

#include <stddef.h>
#include <string.h>

#include "ostd/new.hh"
#include "ostd/types.hh"
#include "ostd/utility.hh"
#include "ostd/type_traits.hh"

namespace ostd {

struct InputRangeTag {};
struct OutputRangeTag {};
struct ForwardRangeTag: InputRangeTag {};
struct BidirectionalRangeTag: ForwardRangeTag {};
struct RandomAccessRangeTag: BidirectionalRangeTag {};
struct FiniteRandomAccessRangeTag: RandomAccessRangeTag {};
struct ContiguousRangeTag: FiniteRandomAccessRangeTag {};

template<typename T> struct RangeHalf;

#define OSTD_RANGE_TRAIT(Name) \
namespace detail { \
    template<typename T> \
    struct Range##Name##Test { \
        template<typename U> static char test(RemoveReference<typename U::Name> *); \
        template<typename U> static  int test(...); \
        static constexpr bool value = (sizeof(test<T>(0)) == sizeof(char)); \
    }; \
    template<typename T, bool = Range##Name##Test<T>::value> \
    struct Range##Name##Base {}; \
    template<typename T> \
    struct Range##Name##Base<T, true> { \
        using Type = typename T::Name; \
    }; \
} \
template<typename T> \
using Range##Name = typename detail::Range##Name##Base<T>::Type;

OSTD_RANGE_TRAIT(Category)
OSTD_RANGE_TRAIT(Size)
OSTD_RANGE_TRAIT(Value)
OSTD_RANGE_TRAIT(Reference)
OSTD_RANGE_TRAIT(Difference)

#undef OSTD_RANGE_TRAIT

namespace detail {
    template<typename U> static char is_range_test(typename U::Category *,
                                                   typename U::Size *,
                                                   typename U::Difference *,
                                                   typename U::Value *,
                                                   RemoveReference<
                                                       typename U::Reference
                                                   > *);
    template<typename U> static int is_range_test(...);

    template<typename T> constexpr bool IsRangeTest
        = (sizeof(is_range_test<T>(0, 0, 0, 0, 0)) == sizeof(char));
}

// is input range

namespace detail {
    template<typename T> constexpr bool IsInputRangeCore
        = IsConvertible<RangeCategory<T>, InputRangeTag>;

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsInputRangeBase = false;

    template<typename T>
    constexpr bool IsInputRangeBase<T, true> = detail::IsInputRangeCore<T>;
}

template<typename T>
constexpr bool IsInputRange = detail::IsInputRangeBase<T>;

// is forward range

namespace detail {
    template<typename T> constexpr bool IsForwardRangeCore
        = IsConvertible<RangeCategory<T>, ForwardRangeTag>;

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsForwardRangeBase = false;

    template<typename T>
    constexpr bool IsForwardRangeBase<T, true> = detail::IsForwardRangeCore<T>;
}

template<typename T>
constexpr bool IsForwardRange = detail::IsForwardRangeBase<T>;

// is bidirectional range

namespace detail {
    template<typename T> constexpr bool IsBidirectionalRangeCore
        = IsConvertible<RangeCategory<T>, BidirectionalRangeTag>;

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsBidirectionalRangeBase = false;

    template<typename T>
    constexpr bool IsBidirectionalRangeBase<T, true> =
        detail::IsBidirectionalRangeCore<T>;
}

template<typename T> constexpr bool IsBidirectionalRange
    = detail::IsBidirectionalRangeBase<T>;

// is random access range

namespace detail {
    template<typename T> constexpr bool IsRandomAccessRangeCore
        = IsConvertible<RangeCategory<T>, RandomAccessRangeTag>;

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsRandomAccessRangeBase = false;

    template<typename T>
    constexpr bool IsRandomAccessRangeBase<T, true> =
        detail::IsRandomAccessRangeCore<T>;
}

template<typename T> constexpr bool IsRandomAccessRange
    = detail::IsRandomAccessRangeBase<T>;

// is finite random access range

namespace detail {
    template<typename T> constexpr bool IsFiniteRandomAccessRangeCore
        = IsConvertible<RangeCategory<T>, FiniteRandomAccessRangeTag>;

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsFiniteRandomAccessRangeBase = false;

    template<typename T>
    constexpr bool IsFiniteRandomAccessRangeBase<T, true> =
        detail::IsFiniteRandomAccessRangeCore<T>;
}

template<typename T> constexpr bool IsFiniteRandomAccessRange
    = detail::IsFiniteRandomAccessRangeBase<T>;

// is infinite random access range

template<typename T> constexpr bool IsInfiniteRandomAccessRange
    = IsRandomAccessRange<T> && !IsFiniteRandomAccessRange<T>;

// is contiguous range

namespace detail {
    template<typename T> constexpr bool IsContiguousRangeCore
        = IsConvertible<RangeCategory<T>, ContiguousRangeTag>;

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsContiguousRangeBase = false;

    template<typename T>
    constexpr bool IsContiguousRangeBase<T, true> =
        detail::IsContiguousRangeCore<T>;
}

template<typename T> constexpr bool IsContiguousRange
    = detail::IsContiguousRangeBase<T>;

// is output range

namespace detail {
    template<typename T, typename P>
    struct OutputRangeTest {
        template<typename U, bool (U::*)(P)> struct Test {};
        template<typename U> static char test(Test<U, &U::put> *);
        template<typename U> static  int test(...);
        static constexpr bool value = (sizeof(test<T>(0)) == sizeof(char));
    };

    template<typename T> constexpr bool IsOutputRangeCore
        = IsConvertible<RangeCategory<T>, OutputRangeTag> ||
          (IsInputRange<T> &&
              (detail::OutputRangeTest<T, const RangeValue<T>  &>::value ||
               detail::OutputRangeTest<T,       RangeValue<T> &&>::value ||
               detail::OutputRangeTest<T,       RangeValue<T>   >::value));

    template<typename T, bool = detail::IsRangeTest<T>>
    constexpr bool IsOutputRangeBase = false;

    template<typename T>
    constexpr bool IsOutputRangeBase<T, true> = detail::IsOutputRangeCore<T>;
}

template<typename T> constexpr bool IsOutputRange = detail::IsOutputRangeBase<T>;

namespace detail {
    // range iterator

    template<typename T>
    struct RangeIterator {
        RangeIterator(): p_range() {}
        explicit RangeIterator(const T &range) {
            ::new(&get_ref()) T(range);
        }
        explicit RangeIterator(T &&range) {
            ::new(&get_ref()) T(move(range));
        }
        RangeIterator &operator++() {
            get_ref().pop_front();
            return *this;
        }
        RangeReference<T> operator*() const {
            return get_ref().front();
        }
        bool operator!=(RangeIterator) const { return !get_ref().empty(); }
    private:
        T &get_ref() { return *((T *)&p_range); }
        const T &get_ref() const { return *((T *)&p_range); }
        AlignedStorage<sizeof(T), alignof(T)> p_range;
    };
}

// range half

template<typename T> struct HalfRange;

namespace detail {
    template<typename R, bool = IsBidirectionalRange<typename R::Range>>
    struct RangeAdd;

    template<typename R>
    struct RangeAdd<R, true> {
        using Diff = RangeDifference<typename R::Range>;

        static Diff add_n(R &half, Diff n) {
            if (n < 0) return -half.prev_n(n);
            return half.next_n(n);
        }
        static Diff sub_n(R &half, Diff n) {
            if (n < 0) return -half.next_n(n);
            return half.prev_n(n);
        }
    };

    template<typename R>
    struct RangeAdd<R, false> {
        using Diff = RangeDifference<typename R::Range>;

        static Diff add_n(R &half, Diff n) {
            if (n < 0) return 0;
            return half.next_n(n);
        }
        static Diff sub_n(R &half, Diff n) {
            if (n < 0) return 0;
            return half.prev_n(n);
        }
    };
}

template<typename T>
struct RangeHalf {
private:
    T p_range;
public:
    using Range = T;

    RangeHalf() = delete;
    RangeHalf(const T &range): p_range(range) {}

    template<typename U, typename = EnableIf<IsConvertible<U, T>>>
    RangeHalf(const RangeHalf<U> &half): p_range(half.p_range) {}

    RangeHalf(const RangeHalf &half): p_range(half.p_range) {}
    RangeHalf(RangeHalf &&half): p_range(move(half.p_range)) {}

    RangeHalf &operator=(const RangeHalf &half) {
        p_range = half.p_range;
        return *this;
    }

    RangeHalf &operator=(RangeHalf &&half) {
        p_range = move(half.p_range);
        return *this;
    }

    bool next() { return p_range.pop_front(); }
    bool prev() { return p_range.push_front(); }

    RangeSize<T> next_n(RangeSize<T> n) {
        return p_range.pop_front_n(n);
    }
    RangeSize<T> prev_n(RangeSize<T> n) {
        return p_range.push_front_n(n);
    }

    RangeDifference<T> add_n(RangeDifference<T> n) {
        return detail::RangeAdd<RangeHalf<T>>::add_n(*this, n);
    }
    RangeDifference<T> sub_n(RangeDifference<T> n) {
        return detail::RangeAdd<RangeHalf<T>>::sub_n(*this, n);
    }

    RangeReference<T> get() const {
        return p_range.front();
    }

    RangeDifference<T> distance(const RangeHalf &half) const {
        return p_range.distance_front(half.p_range);
    }

    bool equals(const RangeHalf &half) const {
        return p_range.equals_front(half.p_range);
    }

    bool operator==(const RangeHalf &half) const {
        return equals(half);
    }
    bool operator!=(const RangeHalf &half) const {
        return !equals(half);
    }

    /* iterator like interface */

    RangeReference<T> operator*() const {
        return get();
    }

    RangeReference<T> operator[](RangeSize<T> idx) const {
        return p_range[idx];
    }

    RangeHalf &operator++() {
        next();
        return *this;
    }
    RangeHalf operator++(int) {
        RangeHalf tmp(*this);
        next();
        return tmp;
    }

    RangeHalf &operator--() {
        prev();
        return *this;
    }
    RangeHalf operator--(int) {
        RangeHalf tmp(*this);
        prev();
        return tmp;
    }

    RangeHalf operator+(RangeDifference<T> n) const {
        RangeHalf tmp(*this);
        tmp.add_n(n);
        return tmp;
    }
    RangeHalf operator-(RangeDifference<T> n) const {
        RangeHalf tmp(*this);
        tmp.sub_n(n);
        return tmp;
    }

    RangeHalf &operator+=(RangeDifference<T> n) {
        add_n(n);
        return *this;
    }
    RangeHalf &operator-=(RangeDifference<T> n) {
        sub_n(n);
        return *this;
    }

    T iter() const { return p_range; }

    HalfRange<RangeHalf> iter(const RangeHalf &other) const {
        return HalfRange<RangeHalf>(*this, other);
    }

    RangeValue<T> *data() { return p_range.data(); }
    const RangeValue<T> *data() const { return p_range.data(); }
};

template<typename R>
RangeDifference<R> operator-(const R &lhs, const R &rhs) {
    return rhs.distance(lhs);
}

namespace detail {
    template<typename R>
    RangeSize<R> pop_front_n(R &range, RangeSize<R> n) {
        for (RangeSize<R> i = 0; i < n; ++i)
            if (!range.pop_front()) return i;
        return n;
    }

    template<typename R>
    RangeSize<R> pop_back_n(R &range, RangeSize<R> n) {
        for (RangeSize<R> i = 0; i < n; ++i)
            if (!range.pop_back()) return i;
        return n;
    }

    template<typename R>
    RangeSize<R> push_front_n(R &range, RangeSize<R> n) {
        for (RangeSize<R> i = 0; i < n; ++i)
            if (!range.push_front()) return i;
        return n;
    }

    template<typename R>
    RangeSize<R> push_back_n(R &range, RangeSize<R> n) {
        for (RangeSize<R> i = 0; i < n; ++i)
            if (!range.push_back()) return i;
        return n;
    }
}

template<typename> struct ReverseRange;
template<typename> struct MoveRange;

template<typename B, typename C, typename V, typename R = V &,
         typename S = Size, typename D = Ptrdiff
> struct InputRange {
    using Category = C;
    using Size = S;
    using Difference = D;
    using Value = V;
    using Reference = R;

    detail::RangeIterator<B> begin() const {
        return detail::RangeIterator<B>((const B &)*this);
    }
    detail::RangeIterator<B> end() const {
        return detail::RangeIterator<B>();
    }

    Size pop_front_n(Size n) {
        return detail::pop_front_n<B>(*((B *)this), n);
    }

    Size pop_back_n(Size n) {
        return detail::pop_back_n<B>(*((B *)this), n);
    }

    Size push_front_n(Size n) {
        return detail::push_front_n<B>(*((B *)this), n);
    }

    Size push_back_n(Size n) {
        return detail::push_back_n<B>(*((B *)this), n);
    }

    B iter() const {
        return B(*((B *)this));
    }

    ReverseRange<B> reverse() const {
        return ReverseRange<B>(iter());
    }

    MoveRange<B> movable() const {
        return MoveRange<B>(iter());
    }

    RangeHalf<B> half() const {
        return RangeHalf<B>(iter());
    }

    Size put_n(const Value *p, Size n) {
        B &r = *((B *)this);
        Size on = n;
        for (; n && r.put(*p++); --n);
        return (on - n);
    }

    template<typename OR>
    EnableIf<IsOutputRange<OR>, Size> copy(OR &&orange, Size n = -1) {
        B r(*((B *)this));
        Size on = n;
        for (; n && !r.empty(); --n) {
            if (!orange.put(r.front()))
                break;
            r.pop_front();
        }
        return (on - n);
    }

    Size copy(RemoveCv<Value> *p, Size n = -1) {
        B r(*((B *)this));
        Size on = n;
        for (; n && !r.empty(); --n) {
            *p++ = r.front();
            r.pop_front();
        }
        return (on - n);
    }

    /* iterator like interface operating on the front part of the range
     * this is sometimes convenient as it can be used within expressions */

    Reference operator*() const {
        return ((B *)this)->front();
    }

    B &operator++() {
        ((B *)this)->pop_front();
        return *((B *)this);
    }
    B operator++(int) {
        B tmp(*((const B *)this));
        ((B *)this)->pop_front();
        return tmp;
    }

    B &operator--() {
        ((B *)this)->push_front();
        return *((B *)this);
    }
    B operator--(int) {
        B tmp(*((const B *)this));
        ((B *)this)->push_front();
        return tmp;
    }

    B operator+(Difference n) const {
        B tmp(*((const B *)this));
        tmp.pop_front_n(n);
        return tmp;
    }
    B operator-(Difference n) const {
        B tmp(*((const B *)this));
        tmp.push_front_n(n);
        return tmp;
    }

    B &operator+=(Difference n) {
        ((B *)this)->pop_front_n(n);
        return *((B *)this);
    }
    B &operator-=(Difference n) {
        ((B *)this)->push_front_n(n);
        return *((B *)this);
    }

    /* universal bool operator */

    explicit operator bool() const { return !((B *)this)->empty(); }
};

template<typename T>
auto iter(T &r) -> decltype(r.iter()) {
    return r.iter();
}

template<typename T>
auto iter(const T &r) -> decltype(r.iter()) {
    return r.iter();
}

template<typename T>
auto citer(const T &r) -> decltype(r.iter()) {
    return r.iter();
}

template<typename B, typename V, typename R = V &,
         typename S = Size, typename D = Ptrdiff
> struct OutputRange {
    using Category = OutputRangeTag;
    using Size = S;
    using Difference = D;
    using Value = V;
    using Reference = R;

    Size put_n(const Value *p, Size n) {
        B &r = *((B *)this);
        Size on = n;
        for (; n && r.put(*p++); --n);
        return (on - n);
    }
};

template<typename T>
struct HalfRange: InputRange<HalfRange<T>,
    RangeCategory<typename T::Range>,
    RangeValue<typename T::Range>,
    RangeReference<typename T::Range>,
    RangeSize<typename T::Range>,
    RangeDifference<typename T::Range>
> {
private:
    using Rtype = typename T::Range;
    T p_beg;
    T p_end;
public:
    HalfRange() = delete;
    HalfRange(const HalfRange &range): p_beg(range.p_beg),
        p_end(range.p_end) {}
    HalfRange(HalfRange &&range): p_beg(move(range.p_beg)),
        p_end(move(range.p_end)) {}
    HalfRange(const T &beg, const T &end): p_beg(beg),
        p_end(end) {}
    HalfRange(T &&beg, T &&end): p_beg(move(beg)),
        p_end(move(end)) {}

    HalfRange &operator=(const HalfRange &range) {
        p_beg = range.p_beg;
        p_end = range.p_end;
        return *this;
    }

    HalfRange &operator=(HalfRange &&range) {
        p_beg = move(range.p_beg);
        p_end = move(range.p_end);
        return *this;
    }

    bool empty() const { return p_beg == p_end; }

    bool pop_front() {
        if (empty()) return false;
        return p_beg.next();
    }
    bool push_front() {
        return p_beg.prev();
    }
    bool pop_back() {
        if (empty()) return false;
        return p_end.prev();
    }
    bool push_back() {
        return p_end.next();
    }

    RangeReference<Rtype> front() const { return *p_beg; }
    RangeReference<Rtype> back() const { return *(p_end - 1); }

    bool equals_front(const HalfRange &range) const {
        return p_beg == range.p_beg;
    }
    bool equals_back(const HalfRange &range) const {
        return p_end == range.p_end;
    }

    RangeDifference<Rtype> distance_front(const HalfRange &range) const {
        return range.p_beg - p_beg;
    }
    RangeDifference<Rtype> distance_back(const HalfRange &range) const {
        return range.p_end - p_end;
    }

    RangeSize<Rtype> size() const { return p_end - p_beg; }

    HalfRange<Rtype>
    slice(RangeSize<Rtype> start, RangeSize<Rtype> end) const {
        return HalfRange<Rtype>(p_beg + start, p_beg + end);
    }

    RangeReference<Rtype> operator[](RangeSize<Rtype> idx) const {
        return p_beg[idx];
    }

    bool put(const RangeValue<Rtype> &v) {
        return p_beg.range().put(v);
    }
    bool put(RangeValue<Rtype> &&v) {
        return p_beg.range().put(move(v));
    }

    RangeValue<Rtype> *data() { return p_beg.data(); }
    const RangeValue<Rtype> *data() const { return p_beg.data(); }
};

template<typename T>
struct ReverseRange: InputRange<ReverseRange<T>,
    CommonType<RangeCategory<T>, FiniteRandomAccessRangeTag>,
    RangeValue<T>, RangeReference<T>, RangeSize<T>, RangeDifference<T>
> {
private:
    using Rref = RangeReference<T>;
    using Rsize = RangeSize<T>;

    T p_range;

public:
    ReverseRange() = delete;
    ReverseRange(const T &range): p_range(range) {}
    ReverseRange(const ReverseRange &it): p_range(it.p_range) {}
    ReverseRange(ReverseRange &&it): p_range(move(it.p_range)) {}

    ReverseRange &operator=(const ReverseRange &v) {
        p_range = v.p_range;
        return *this;
    }
    ReverseRange &operator=(ReverseRange &&v) {
        p_range = move(v.p_range);
        return *this;
    }
    ReverseRange &operator=(const T &v) {
        p_range = v;
        return *this;
    }
    ReverseRange &operator=(T &&v) {
        p_range = move(v);
        return *this;
    }

    bool empty() const { return p_range.empty(); }
    Rsize size() const { return p_range.size(); }

    bool equals_front(const ReverseRange &r) const {
    return p_range.equals_back(r.p_range);
    }
    bool equals_back(const ReverseRange &r) const {
        return p_range.equals_front(r.p_range);
    }

    RangeDifference<T> distance_front(const ReverseRange &r) const {
        return -p_range.distance_back(r.p_range);
    }
    RangeDifference<T> distance_back(const ReverseRange &r) const {
        return -p_range.distance_front(r.p_range);
    }

    bool pop_front() { return p_range.pop_back(); }
    bool pop_back() { return p_range.pop_front(); }

    bool push_front() { return p_range.push_back(); }
    bool push_back() { return p_range.push_front(); }

    Rsize pop_front_n(Rsize n) { return p_range.pop_front_n(n); }
    Rsize pop_back_n(Rsize n) { return p_range.pop_back_n(n); }

    Rsize push_front_n(Rsize n) { return p_range.push_front_n(n); }
    Rsize push_back_n(Rsize n) { return p_range.push_back_n(n); }

    Rref front() const { return p_range.back(); }
    Rref back() const { return p_range.front(); }

    Rref operator[](Rsize i) const { return p_range[size() - i - 1]; }

    ReverseRange<T> slice(Rsize start, Rsize end) const {
        Rsize len = p_range.size();
        return ReverseRange<T>(p_range.slice(len - end, len - start));
    }
};

template<typename T>
struct MoveRange: InputRange<MoveRange<T>,
    CommonType<RangeCategory<T>, FiniteRandomAccessRangeTag>,
    RangeValue<T>, RangeValue<T> &&, RangeSize<T>, RangeDifference<T>
> {
private:
    using Rval = RangeValue<T>;
    using Rref = RangeValue<T> &&;
    using Rsize = RangeSize<T>;

    T p_range;

public:
    MoveRange() = delete;
    MoveRange(const T &range): p_range(range) {}
    MoveRange(const MoveRange &it): p_range(it.p_range) {}
    MoveRange(MoveRange &&it): p_range(move(it.p_range)) {}

    MoveRange &operator=(const MoveRange &v) {
        p_range = v.p_range;
        return *this;
    }
    MoveRange &operator=(MoveRange &&v) {
        p_range = move(v.p_range);
        return *this;
    }
    MoveRange &operator=(const T &v) {
        p_range = v;
        return *this;
    }
    MoveRange &operator=(T &&v) {
        p_range = move(v);
        return *this;
    }

    bool empty() const { return p_range.empty(); }
    Rsize size() const { return p_range.size(); }

    bool equals_front(const MoveRange &r) const {
        return p_range.equals_front(r.p_range);
    }
    bool equals_back(const MoveRange &r) const {
        return p_range.equals_back(r.p_range);
    }

    RangeDifference<T> distance_front(const MoveRange &r) const {
        return p_range.distance_front(r.p_range);
    }
    RangeDifference<T> distance_back(const MoveRange &r) const {
        return p_range.distance_back(r.p_range);
    }

    bool pop_front() { return p_range.pop_front(); }
    bool pop_back() { return p_range.pop_back(); }

    bool push_front() { return p_range.push_front(); }
    bool push_back() { return p_range.push_back(); }

    Rsize pop_front_n(Rsize n) { return p_range.pop_front_n(n); }
    Rsize pop_back_n(Rsize n) { return p_range.pop_back_n(n); }

    Rsize push_front_n(Rsize n) { return p_range.push_front_n(n); }
    Rsize push_back_n(Rsize n) { return p_range.push_back_n(n); }

    Rref front() const { return move(p_range.front()); }
    Rref back() const { return move(p_range.back()); }

    Rref operator[](Rsize i) const { return move(p_range[i]); }

    MoveRange<T> slice(Rsize start, Rsize end) const {
        return MoveRange<T>(p_range.slice(start, end));
    }

    bool put(const Rval &v) { return p_range.put(v); }
    bool put(Rval &&v) { return p_range.put(move(v)); }
};

template<typename T>
struct NumberRange: InputRange<NumberRange<T>, ForwardRangeTag, T, T> {
    NumberRange() = delete;
    NumberRange(const NumberRange &it): p_a(it.p_a), p_b(it.p_b),
        p_step(it.p_step) {}
    NumberRange(T a, T b, T step = T(1)): p_a(a), p_b(b),
        p_step(step) {}
    NumberRange(T v): p_a(0), p_b(v), p_step(1) {}

    bool empty() const { return p_a * p_step >= p_b * p_step; }

    bool equals_front(const NumberRange &range) const {
        return p_a == range.p_a;
    }

    bool pop_front() { p_a += p_step; return true; }
    T front() const { return p_a; }

private:
    T p_a, p_b, p_step;
};

template<typename T>
NumberRange<T> range(T a, T b, T step = T(1)) {
    return NumberRange<T>(a, b, step);
}

template<typename T>
NumberRange<T> range(T v) {
    return NumberRange<T>(v);
}

template<typename T>
struct PointerRange: InputRange<PointerRange<T>, ContiguousRangeTag, T> {
private:
    struct Nat {};

public:
    PointerRange(): p_beg(nullptr), p_end(nullptr) {}

    template<typename U>
    PointerRange(T *beg, U end, EnableIf<
        (IsPointer<U> || IsNullPointer<U>) && IsConvertible<U, T *>, Nat
    > = Nat()): p_beg(beg), p_end(end) {}

    PointerRange(T *beg, Size n): p_beg(beg), p_end(beg + n) {}

    template<typename U, typename = EnableIf<IsConvertible<U *, T *>>>
    PointerRange(const PointerRange<U> &v): p_beg(&v[0]), p_end(&v[v.size()]) {}

    PointerRange &operator=(const PointerRange &v) {
        p_beg = v.p_beg;
        p_end = v.p_end;
        return *this;
    }

    /* satisfy InputRange / ForwardRange */
    bool empty() const { return p_beg == p_end; }

    bool pop_front() {
        if (p_beg == p_end) return false;
        ++p_beg;
        return true;
    }
    bool push_front() {
        --p_beg; return true;
    }

    Size pop_front_n(Size n) {
        Size olen = p_end - p_beg;
        p_beg += n;
        if (p_beg > p_end) {
            p_beg = p_end;
            return olen;
        }
        return n;
    }

    Size push_front_n(Size n) {
        p_beg -= n; return true;
    }

    T &front() const { return *p_beg; }

    bool equals_front(const PointerRange &range) const {
        return p_beg == range.p_beg;
    }

    Ptrdiff distance_front(const PointerRange &range) const {
        return range.p_beg - p_beg;
    }

    /* satisfy BidirectionalRange */
    bool pop_back() {
        if (p_end == p_beg) return false;
        --p_end;
        return true;
    }
    bool push_back() {
        ++p_end; return true;
    }

    Size pop_back_n(Size n) {
        Size olen = p_end - p_beg;
        p_end -= n;
        if (p_end < p_beg) {
            p_end = p_beg;
            return olen;
        }
        return n;
    }

    Size push_back_n(Size n) {
        p_end += n; return true;
    }

    T &back() const { return *(p_end - 1); }

    bool equals_back(const PointerRange &range) const {
        return p_end == range.p_end;
    }

    Ptrdiff distance_back(const PointerRange &range) const {
        return range.p_end - p_end;
    }

    /* satisfy FiniteRandomAccessRange */
    Size size() const { return p_end - p_beg; }

    PointerRange slice(Size start, Size end) const {
        return PointerRange(p_beg + start, p_beg + end);
    }

    T &operator[](Size i) const { return p_beg[i]; }

    /* satisfy OutputRange */
    bool put(const T &v) {
        if (empty()) return false;
        *(p_beg++) = v;
        return true;
    }
    bool put(T &&v) {
        if (empty()) return false;
        *(p_beg++) = move(v);
        return true;
    }

    Size put_n(const T *p, Size n) {
        Size ret = size();
        if (n < ret) ret = n;
        if (IsPod<T>) {
            memcpy(p_beg, p, ret * sizeof(T));
            p_beg += ret;
            return ret;
        }
        for (Size i = ret; i; --i)
            *p_beg++ = *p++;
        return ret;
    }

    template<typename R>
    EnableIf<IsOutputRange<R>, Size> copy(R &&orange, Size n = -1) {
        Size c = size();
        if (n < c) c = n;
        return orange.put_n(p_beg, c);
    }

    Size copy(RemoveCv<T> *p, Size n = -1) {
        Size c = size();
        if (n < c) c = n;
        if (IsPod<T>) {
            memcpy(p_beg, data(), c * sizeof(T));
            return c;
        }
        return copy(PointerRange(p, c), c);
    }

    T *data() { return p_beg; }
    const T *data() const { return p_beg; }

private:
    T *p_beg, *p_end;
};

template<typename T, Size N>
PointerRange<T> iter(T (&array)[N]) {
    return PointerRange<T>(array, N);
}

template<typename T, Size N>
PointerRange<const T> iter(const T (&array)[N]) {
    return PointerRange<const T>(array, N);
}

namespace detail {
    struct PtrNat {};
}

template<typename T, typename U>
PointerRange<T> iter(T *a, U b, EnableIf<
    (IsPointer<U> || IsNullPointer<U>) && IsConvertible<U, T *>, detail::PtrNat
> = detail::PtrNat()) {
    return PointerRange<T>(a, b);
}

template<typename T>
PointerRange<T> iter(T *a, ostd::Size b) {
    return PointerRange<T>(a, b);
}

template<typename T, typename S>
struct EnumeratedValue {
    S index;
    T value;
};

template<typename T>
struct EnumeratedRange: InputRange<EnumeratedRange<T>,
    CommonType<RangeCategory<T>, ForwardRangeTag>, RangeValue<T>,
    EnumeratedValue<RangeReference<T>, RangeSize<T>>,
    RangeSize<T>
> {
private:
    using Rref = RangeReference<T>;
    using Rsize = RangeSize<T>;

    T p_range;
    Rsize p_index;

public:
    EnumeratedRange() = delete;

    EnumeratedRange(const T &range): p_range(range), p_index(0) {}

    EnumeratedRange(const EnumeratedRange &it):
        p_range(it.p_range), p_index(it.p_index) {}

    EnumeratedRange(EnumeratedRange &&it):
        p_range(move(it.p_range)), p_index(it.p_index) {}

    EnumeratedRange &operator=(const EnumeratedRange &v) {
        p_range = v.p_range;
        p_index = v.p_index;
        return *this;
    }
    EnumeratedRange &operator=(EnumeratedRange &&v) {
        p_range = move(v.p_range);
        p_index = v.p_index;
        return *this;
    }
    EnumeratedRange &operator=(const T &v) {
        p_range = v;
        p_index = 0;
        return *this;
    }
    EnumeratedRange &operator=(T &&v) {
        p_range = move(v);
        p_index = 0;
        return *this;
    }

    bool empty() const { return p_range.empty(); }

    bool equals_front(const EnumeratedRange &r) const {
        return p_range.equals_front(r.p_range);
    }

    bool pop_front() {
        if (p_range.pop_front()) {
            ++p_index;
            return true;
        }
        return false;
    }

    Rsize pop_front_n(Rsize n) {
        Rsize ret = p_range.pop_front_n(n);
        p_index += ret;
        return ret;
    }

    EnumeratedValue<Rref, Rsize> front() const {
        return EnumeratedValue<Rref, Rsize> { p_index, p_range.front() };
    }
};

template<typename T>
EnumeratedRange<T> enumerate(const T &it) {
    return EnumeratedRange<T>(it);
}

template<typename T>
struct TakeRange: InputRange<TakeRange<T>,
    CommonType<RangeCategory<T>, ForwardRangeTag>,
    RangeValue<T>, RangeReference<T>, RangeSize<T>
> {
private:
    T p_range;
    RangeSize<T> p_remaining;
public:
    TakeRange() = delete;
    TakeRange(const T &range, RangeSize<T> rem): p_range(range),
        p_remaining(rem) {}
    TakeRange(const TakeRange &it): p_range(it.p_range),
        p_remaining(it.p_remaining) {}
    TakeRange(TakeRange &&it): p_range(move(it.p_range)),
        p_remaining(it.p_remaining) {}

    TakeRange &operator=(const TakeRange &v) {
        p_range = v.p_range; p_remaining = v.p_remaining; return *this;
    }
    TakeRange &operator=(TakeRange &&v) {
        p_range = move(v.p_range);
        p_remaining = v.p_remaining;
        return *this;
    }

    bool empty() const { return (p_remaining <= 0) || p_range.empty(); }

    bool pop_front() {
        if (p_range.pop_front()) {
            --p_remaining;
            return true;
        }
        return false;
    }

    RangeSize<T> pop_front_n(RangeSize<T> n) {
        RangeSize<T> ret = p_range.pop_front_n(n);
        p_remaining -= ret;
        return ret;
    }

    RangeReference<T> front() const { return p_range.front(); }

    bool equals_front(const TakeRange &r) const {
        return p_range.equals_front(r.p_range);
    }
};

template<typename T>
TakeRange<T> take(const T &it, RangeSize<T> n) {
    return TakeRange<T>(it, n);
}

template<typename T>
struct ChunksRange: InputRange<ChunksRange<T>,
    CommonType<RangeCategory<T>, ForwardRangeTag>,
    TakeRange<T>, TakeRange<T>, RangeSize<T>
> {
private:
    T p_range;
    RangeSize<T> p_chunksize;
public:
    ChunksRange() = delete;
    ChunksRange(const T &range, RangeSize<T> chs): p_range(range),
        p_chunksize(chs) {}
    ChunksRange(const ChunksRange &it): p_range(it.p_range),
        p_chunksize(it.p_chunksize) {}
    ChunksRange(ChunksRange &&it): p_range(move(it.p_range)),
        p_chunksize(it.p_chunksize) {}

    ChunksRange &operator=(const ChunksRange &v) {
        p_range = v.p_range; p_chunksize = v.p_chunksize; return *this;
    }
    ChunksRange &operator=(ChunksRange &&v) {
        p_range = move(v.p_range);
        p_chunksize = v.p_chunksize;
        return *this;
    }

    bool empty() const { return p_range.empty(); }

    bool equals_front(const ChunksRange &r) const {
        return p_range.equals_front(r.p_range);
    }

    bool pop_front() { return p_range.pop_front_n(p_chunksize) > 0; }
    RangeSize<T> pop_front_n(RangeSize<T> n) {
        return p_range.pop_front_n(p_chunksize * n) / p_chunksize;
    }

    TakeRange<T> front() const { return take(p_range, p_chunksize); }
};

template<typename T>
ChunksRange<T> chunks(const T &it, RangeSize<T> chs) {
    return ChunksRange<T>(it, chs);
}

template<typename T>
struct AppenderRange: OutputRange<AppenderRange<T>, typename T::Value,
    typename T::Reference, typename T::Size, typename T::Difference> {
    AppenderRange(): p_data() {}
    AppenderRange(const T &v): p_data(v) {}
    AppenderRange(T &&v): p_data(move(v)) {}
    AppenderRange(const AppenderRange &v): p_data(v.p_data) {}
    AppenderRange(AppenderRange &&v): p_data(move(v.p_data)) {}

    AppenderRange &operator=(const AppenderRange &v) {
        p_data = v.p_data;
        return *this;
    }

    AppenderRange &operator=(AppenderRange &&v) {
        p_data = move(v.p_data);
        return *this;
    }

    AppenderRange &operator=(const T &v) {
        p_data = v;
        return *this;
    }

    AppenderRange &operator=(T &&v) {
        p_data = move(v);
        return *this;
    }

    void clear() { p_data.clear(); }

    void reserve(typename T::Size cap) { p_data.reserve(cap); }
    void resize(typename T::Size len) { p_data.resize(len); }

    typename T::Size size() const { return p_data.size(); }
    typename T::Size capacity() const { return p_data.capacity(); }

    bool put(typename T::ConstReference v) {
        p_data.push(v);
        return true;
    }

    bool put(typename T::Value &&v) {
        p_data.push(move(v));
        return true;
    }

    T &get() { return p_data; }
private:
    T p_data;
};

template<typename T>
AppenderRange<T> appender() {
    return AppenderRange<T>();
}

template<typename T>
AppenderRange<T> appender(T &&v) {
    return AppenderRange<T>(forward<T>(v));
}

// range of
template<typename T> using RangeOf = decltype(iter(declval<T>()));

} /* namespace ostd */

#endif