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iterator.h
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iterator.h
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#pragma once
#include <optional>
#include <fstream>
#include <cassert>
#include <vector>
#include <iostream>
#include <functional>
#include <type_traits>
#include "types.h"
//template<typename T>
//concept bool Iterator = requires(T a) {
//typename T::value_type;
//
//{ a.next() } -> optional<typename T::value_type>;
//};
namespace {
//
// This unused class represents an interface, that generic Iterator must implement.
//
// template<typename T>
// class Iterator {
// public:
// using value_type = T;
// optional<T> next() = 0;
// };
template<typename I>
struct is_iterator {
constexpr static bool value =
std::is_same<decltype(std::declval<I>().next()), optional<typename I::value_type>>::value &&
// return value of next and optional<value_type> match
!std::is_reference<typename I::value_type>::value; // value_type is not a reference
};
template<typename Iter, typename Func>
class MapIterator {
private:
Iter iter;
Func func;
public:
using value_type = decltype(func(std::declval<typename Iter::value_type>()));
static_assert(is_iterator<Iter>::value);
static_assert(std::is_invocable<Func, typename Iter::value_type>());
MapIterator(const MapIterator &other) = delete;
MapIterator(MapIterator &&old) = default;
MapIterator(Iter &&a, Func &&b) : iter{move(a)}, func{move(b)} {}
auto next() {
auto a = iter.next();
return a ? make_optional(func(move(*a))) : nullopt;
}
};
template<typename Iter, typename Func>
class FilterIterator {
private:
Iter iter;
Func func;
public:
using value_type = typename Iter::value_type;
static_assert(is_iterator<Iter>::value);
static_assert(std::is_invocable_r<bool, Func, value_type>::value);
FilterIterator(const FilterIterator &other) = delete;
FilterIterator(FilterIterator &&old) = default;
FilterIterator(Iter &&a, Func &&b) : iter{move(a)}, func{std::move(b)} {}
optional<value_type> next() {
auto a = iter.next();
return !a.has_value() ? nullopt :
func(*a) ? make_optional(*a) :
next();
}
};
template <class stream>
class StreamLineIterator {
private:
stream in;
public:
using value_type = std::string;
explicit StreamLineIterator(stream &&st) :in{move(st)} {
assert(in.good() && "Broken stream...");
}
explicit StreamLineIterator(stream st, bool _copy): in{st} {
assert(in.good() && "Broken stream...");
};
StreamLineIterator(const StreamLineIterator &old) = delete;
StreamLineIterator(StreamLineIterator &&old) = default;
optional<std::string> next() {
if (in.eof() || in.fail() || in.bad()) {
return nullopt;
} else {
std::string line;
std::getline(in, line);
return optional<std::string>{line};
}
}
};
template<typename ObsoleteIter>
class ObsoleteIteratorConverter {
private:
ObsoleteIter _start;
ObsoleteIter _end;
public:
using value_type = typename std::iterator_traits<ObsoleteIter>::value_type;
static_assert(!std::is_reference<value_type>::value);
static_assert(std::is_same<decltype(_start), decltype(_start++)>::value);
ObsoleteIteratorConverter(const ObsoleteIteratorConverter &other) = delete;
ObsoleteIteratorConverter(ObsoleteIteratorConverter &&old) = default;
ObsoleteIteratorConverter(ObsoleteIter &&start, ObsoleteIter &&ennd) : _start{move(start)},
_end{move(ennd)} {}
optional<value_type> next() {
return _start == _end ?
nullopt :
[&]() {
auto retVal = move(*_start);
_start++;
return make_optional(move(retVal));
}();
}
};
template<typename T>
class IncrementIter {
private:
T state;
public:
IncrementIter(const IncrementIter &other) = delete;
IncrementIter(IncrementIter &&old) = default;
static_assert(std::is_same_v<decltype((*(T*) nullptr)++), T>, "Template type does not implement ++ operator.");
explicit IncrementIter(T &&init) : state{move(init)} {}
using value_type = T;
optional<T> next() {
return make_optional(state++);
}
};
template<typename Iter>
class LimitIterator {
private:
usize count = 0;
usize limit;
Iter iter;
public:
using value_type = typename Iter::value_type;
static_assert(is_iterator<Iter>::value);
LimitIterator(const LimitIterator &other) = delete;
LimitIterator(LimitIterator &&old) = default;
LimitIterator(Iter &&iter, usize limit) : limit{limit}, iter{move(iter)} {}
optional<typename Iter::value_type> next() {
if (count >= limit)
return {};
count++;
return iter.next();
}
};
template<typename Iter1, typename Iter2>
class ZipIterator {
private:
Iter1 iter1;
Iter2 iter2;
public:
static_assert(is_iterator<Iter1>::value);
static_assert(is_iterator<Iter2>::value);
using value_type = std::pair<typename Iter1::value_type, typename Iter2::value_type>;
ZipIterator(const ZipIterator &other) = delete;
ZipIterator(ZipIterator &&old) = default;
ZipIterator(Iter1 &&iter1, Iter2 &&iter2) : iter1{move(iter1)}, iter2{move(iter2)} {}
optional<value_type> next() {
auto a = iter1.next();
auto b = iter2.next();
if (a && b) {
return optional(std::pair{*a, *b});
} else {
return nullopt;
}
}
};
}
struct IOldIteratorEnd {
};
template<typename Iter>
class I {
public:
using value_type = typename Iter::value_type;
private:
optional<Iter> iter;
optional<value_type> last_value_for_oldschool_iter = {};
template <typename OtherIter>
I<OtherIter> wrap_iter(OtherIter&& iter) {
return I<OtherIter>(move(iter));
}
public:
I(I &&old) = default;
I(I &other) = delete;
I(Iter &&iter) : iter{move(iter)} {}
static_assert(is_iterator<Iter>::value);
/**
* The function takes ownership of the data and returns it again.
* @tparam Func Function, which will take ownership of the data and return it again
* @param f
* @return
*/
template<typename Func>
auto map(Func &&f) {
assert(iter);
MapIterator<Iter, Func> mi(move(*iter), move(f));
iter.reset();
return wrap_iter(move(mi));
}
template<typename Func>
auto lazy_for_each(Func &&f) {
assert(iter);
MapIterator mi(move(*iter), [=](value_type p) {
value_type const &r = p;
f(r);
return p;
});
iter.reset();
return wrap_iter(move(mi));
}
template<typename Func>
void into(Func &&f) {
assert(iter);
MapIterator mi(move(*iter), [=](value_type p) {
f(move(p));
return 0;
});
iter.reset();
wrap_iter(move(mi)).exhaust();
}
template<typename Func>
auto filter(Func &&f) {
assert(iter);
FilterIterator<Iter, Func> fi(move(*iter), f);
iter.reset();
return wrap_iter(move(fi));
}
optional<value_type> next() {
assert(iter);
return (*iter).next();
}
auto collect() {
assert(iter);
std::vector<value_type> result;
while (auto a = (*iter).next()) result.push_back(*a);
return result;
}
void exhaust() {
assert(iter);
while (iter->next()) {}
}
auto take(usize count) {
assert(iter);
LimitIterator li(move(*iter), count);
iter.reset();
return wrap_iter(move(li));
}
template<typename Func, typename State>
State fold(Func &&f, State &&s) {
static_assert(!std::is_reference_v<decltype(f(std::declval<typename Iter::value_type>(), std::declval<State>()))>,
"Function returns a reference, but it should return by value.");
static_assert(!std::is_reference_v<State>, "State in fold can't be reference.");
assert(iter);
while (auto a = iter->next()) {
State ss = f(move(*a), move(s));
s = move(ss);
}
return move(s);
}
template<typename Func>
optional<typename Iter::value_type> reduce(Func &&f) {
static_assert(std::is_same_v<typename Iter::value_type, decltype(f(std::declval<typename Iter::value_type>(),
std::declval<typename Iter::value_type>()))>,
"Return type is not the same as iterator type!");
assert(iter);
auto first = iter->next();
if (!first) {
return nullopt;
}
return make_optional(fold(move(f), move(*first)));
}
using iterator = I&;
std::reference_wrapper<I> begin() {
last_value_for_oldschool_iter = next();
return std::reference_wrapper(*this);
}
friend value_type &operator*(std::reference_wrapper<I> & me) {
if (me.get().last_value_for_oldschool_iter)
return *(me.get().last_value_for_oldschool_iter);
else
throw std::range_error("Iterator range overrun!");
}
std::reference_wrapper<I> end() {
// cause the comparison operator will report ending when comparing with anything, we can just return any garbage
return std::reference_wrapper(*this);
}
friend void operator++(std::reference_wrapper<I> & me) {
me.get().last_value_for_oldschool_iter = me.get().next();
}
/**
* Returns whether we run out of values. The comparison is otherwise useless, it's here just for compatibility
* reasons with the archaic C++ iterators.
*/
friend bool operator==(std::reference_wrapper<I> & me, std::reference_wrapper<I> & _) {
return !me.get().last_value_for_oldschool_iter.has_value();
}
/**
* See the operator==
*/
friend bool operator!=(std::reference_wrapper<I>& me, std::reference_wrapper<I>& other) {
return !(me == other);
}
auto enumerate() {
assert(iter);
return wrap_iter(ZipIterator(IncrementIter((usize) 0), move(*iter)));
}
auto sum() {
assert(iter);
return fold([](auto v, auto s) { return v + s; }, (usize) 0);
}
auto sum(typename Iter::value_type initialValue) {
assert(iter);
return fold([](auto v, auto s) { return v + s; }, initialValue);
}
optional<typename Iter::value_type> max() {
assert(iter);
return reduce([](auto a, auto b) { return a > b ? a : b; });
}
template<typename Func>
optional<typename Iter::value_type> max_by(Func &&f) {
assert(iter);
return reduce([=](auto a, auto b) { return f(a) > f(b) ? a : b; });
}
optional<typename Iter::value_type> min() {
assert(iter);
return reduce([](auto a, auto b) { return a < b ? a : b; });
}
template<typename Func>
optional<typename Iter::value_type> min_by(Func &&f) {
assert(iter);
return reduce([=](auto a, auto b) { return f(a) < f(b) ? a : b; });
}
};
namespace Iter {
template<typename T>
auto count_from(T init) {
return I(IncrementIter(move(init)));
}
auto range(usize fromInclusive, usize toExclusive) {
return count_from(fromInclusive).take(toExclusive - fromInclusive);
}
auto range(usize toExclusive) {
return count_from((usize) 0).take(toExclusive);
}
auto file_by_lines(const std::string &file) {
return I(StreamLineIterator<std::ifstream>(std::ifstream(file)));
}
auto stdin_by_lines() {
return I(StreamLineIterator<std::istream&>(std::cin, false));
}
template<typename Iter1, typename Iter2>
auto zip(Iter1 &&iter1, Iter2 &&iter2) {
static_assert(is_iterator<Iter1>::value);
static_assert(is_iterator<Iter2>::value);
return I(move(ZipIterator(move(iter1), move(iter2))));
}
template<typename Container>
auto from(Container &&vec) {
return I(move(ObsoleteIteratorConverter(vec.begin(), vec.end())));
}
template<typename Container>
auto from(Container &vec) {
return I(move(ObsoleteIteratorConverter(vec.begin(), vec.end())));
}
}