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#pragma once
#include "udf_value.h"
#include <yql/essentials/utils/method_index.h>
#include <util/generic/ymath.h>
#include <util/system/platform.h>
#include <util/generic/yexception.h>
#include <util/system/yassert.h>
#include <util/string/hex.h>
namespace NYql {
namespace NUdf {
template<bool HasLength = true>
class TLazyList: public NUdf::TBoxedValue {
struct TIterator: public NUdf::TBoxedValue {
TIterator(i32 from, i32 to)
: From(from), To(to), Curr(Max<i32>())
{
if (To >= From) {
To--; // exclude last
} else {
From--; // exclude first
}
}
private:
bool Skip() override {
if (Curr == Max<i32>()) {
Curr = From;
return true;
}
if (To >= From) {
if (Curr < To) {
++Curr;
return true;
}
} else {
if (Curr > To) {
--Curr;
return true;
}
}
return false;
}
bool Next(NUdf::TUnboxedValue& value) override {
if (!Skip())
return false;
value = NUdf::TUnboxedValuePod(Curr);
return true;
}
i32 From, To, Curr;
};
public:
TLazyList(i32 from, i32 to)
: From_(from), To_(to)
{
}
private:
bool HasFastListLength() const override {
return HasLength;
}
ui64 GetListLength() const override {
if (HasLength)
return Abs(To_ - From_);
Y_ABORT("No length!");
}
bool HasListItems() const override {
return To_ != From_;
}
NUdf::TUnboxedValue GetListIterator() const override {
return NUdf::TUnboxedValuePod(new TIterator(From_, To_));
}
NUdf::IBoxedValuePtr ReverseListImpl(const NUdf::IValueBuilder& builder) const override {
Y_UNUSED(builder);
return new TLazyList(To_, From_);
}
NUdf::IBoxedValuePtr SkipListImpl(const NUdf::IValueBuilder& builder, ui64 count) const override {
Y_UNUSED(builder);
count = std::min<ui64>(count, Abs(To_ - From_));
if (To_ >= From_) {
return new TLazyList(From_ + count, To_);
}
return new TLazyList(From_ - count, To_);
}
NUdf::IBoxedValuePtr TakeListImpl(const NUdf::IValueBuilder& builder, ui64 count) const override {
Y_UNUSED(builder);
count = std::min<ui64>(count, Abs(To_ - From_));
if (To_ >= From_) {
return new TLazyList(From_, From_ + count);
}
return new TLazyList(From_, From_ - count);
}
NUdf::IBoxedValuePtr ToIndexDictImpl(const NUdf::IValueBuilder& builder) const override {
Y_UNUSED(builder);
return nullptr;
}
i32 From_, To_;
};
}
}
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