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#pragma once
#include "typetraits.h"
#include "utility.h"
#include <util/system/yassert.h>
#include <iterator>
/** @file
* Some similar for python xrange(): https://docs.python.org/2/library/functions.html#xrange
* Discussion: https://clubs.at.yandex-team.ru/arcadia/6124
*
* Example usage:
* for (auto i: xrange(MyVector.size())) { // instead for (size_t i = 0; i < MyVector.size(); ++i)
* DoSomething(i, MyVector[i]);
* }
*
* TVector<int> arithmeticSeq = xrange(10); // instead: TVector<int> arithmeticSeq; for(size_t i = 0; i < 10; ++i) { arithmeticSeq.push_back(i); }
*
*/
namespace NPrivate {
template <typename T>
class TSimpleXRange {
using TDiff = decltype(T() - T());
public:
constexpr TSimpleXRange(T start, T finish) noexcept
: Start(start)
, Finish(Max(start, finish))
{
}
class TIterator {
public:
using value_type = T;
using difference_type = TDiff;
using pointer = const T*;
using reference = const T&;
using iterator_category = std::random_access_iterator_tag;
constexpr TIterator(T value) noexcept
: Value(value)
{
}
constexpr T operator*() const noexcept {
return Value;
}
constexpr bool operator!=(const TIterator& other) const noexcept {
return Value != other.Value;
}
constexpr bool operator==(const TIterator& other) const noexcept {
return Value == other.Value;
}
TIterator& operator++() noexcept {
++Value;
return *this;
}
TIterator& operator--() noexcept {
--Value;
return *this;
}
constexpr TDiff operator-(const TIterator& b) const noexcept {
return Value - b.Value;
}
template <typename IntType>
constexpr TIterator operator+(const IntType& b) const noexcept {
return TIterator(Value + b);
}
template <typename IntType>
TIterator& operator+=(const IntType& b) noexcept {
Value += b;
return *this;
}
template <typename IntType>
constexpr TIterator operator-(const IntType& b) const noexcept {
return TIterator(Value - b);
}
template <typename IntType>
TIterator& operator-=(const IntType& b) noexcept {
Value -= b;
return *this;
}
constexpr bool operator<(const TIterator& b) const noexcept {
return Value < b.Value;
}
private:
T Value;
};
using value_type = T;
using iterator = TIterator;
using const_iterator = TIterator;
constexpr TIterator begin() const noexcept {
return TIterator(Start);
}
constexpr TIterator end() const noexcept {
return TIterator(Finish);
}
constexpr T size() const noexcept {
return Finish - Start;
}
template <class Container>
operator Container() const {
return Container(begin(), end());
}
private:
T Start;
T Finish;
};
template <typename T>
class TSteppedXRange {
using TDiff = decltype(T() - T());
public:
constexpr TSteppedXRange(T start, T finish, TDiff step) noexcept
: Start_(start)
, Step_(step)
, Finish_(CalcRealFinish(Start_, finish, Step_))
{
static_assert(std::is_integral<T>::value || std::is_pointer<T>::value, "T should be integral type or pointer");
}
class TIterator {
public:
using value_type = T;
using difference_type = TDiff;
using pointer = const T*;
using reference = const T&;
using iterator_category = std::random_access_iterator_tag;
constexpr TIterator(T value, const TSteppedXRange& parent) noexcept
: Value_(value)
, Parent_(&parent)
{
}
constexpr T operator*() const noexcept {
return Value_;
}
constexpr bool operator!=(const TIterator& other) const noexcept {
return Value_ != other.Value_;
}
constexpr bool operator==(const TIterator& other) const noexcept {
return Value_ == other.Value_;
}
TIterator& operator++() noexcept {
Value_ += Parent_->Step_;
return *this;
}
TIterator& operator--() noexcept {
Value_ -= Parent_->Step_;
return *this;
}
constexpr TDiff operator-(const TIterator& b) const noexcept {
return (Value_ - b.Value_) / Parent_->Step_;
}
template <typename IntType>
constexpr TIterator operator+(const IntType& b) const noexcept {
return TIterator(*this) += b;
}
template <typename IntType>
TIterator& operator+=(const IntType& b) noexcept {
Value_ += b * Parent_->Step_;
return *this;
}
template <typename IntType>
constexpr TIterator operator-(const IntType& b) const noexcept {
return TIterator(*this) -= b;
}
template <typename IntType>
TIterator& operator-=(const IntType& b) noexcept {
Value_ -= b * Parent_->Step_;
return *this;
}
private:
T Value_;
const TSteppedXRange* Parent_;
};
using value_type = T;
using iterator = TIterator;
using const_iterator = TIterator;
constexpr TIterator begin() const noexcept {
return TIterator(Start_, *this);
}
constexpr TIterator end() const noexcept {
return TIterator(Finish_, *this);
}
static T CalcRealFinish(T start, T expFinish, TDiff step) {
Y_ASSERT(step != 0);
if (step > 0) {
if (expFinish > start) {
return start + step * ((expFinish - 1 - start) / step + 1);
}
return start;
}
return start - TSteppedXRange<TDiff>::CalcRealFinish(0, start - expFinish, -step);
}
constexpr T size() const noexcept {
return (Finish_ - Start_) / Step_;
}
template <class Container>
operator Container() const {
return Container(begin(), end());
}
private:
const T Start_;
const TDiff Step_;
const T Finish_;
};
}
/**
* generate arithmetic progression that starts at start with certain step and stop at finish (not including)
*
* @param step must be non-zero
*/
template <typename T>
constexpr ::NPrivate::TSteppedXRange<T> xrange(T start, T finish, decltype(T() - T()) step) noexcept {
return {start, finish, step};
}
/// generate sequence [start; finish)
template <typename T>
constexpr ::NPrivate::TSimpleXRange<T> xrange(T start, T finish) noexcept {
return {start, finish};
}
/// generate sequence [0; finish)
template <typename T>
constexpr auto xrange(T finish) noexcept -> decltype(xrange(T(), finish)) {
return xrange(T(), finish);
}
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