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Added Pythagorean Triples
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@BartoszMilewski
BartoszMilewski committed Apr 17, 2014
1 parent f9f7bbd commit e6ef2a3
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Showing 4 changed files with 293 additions and 384 deletions.
237 changes: 118 additions & 119 deletions PureStream/PureStream.h
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Original file line number Diff line number Diff line change
Expand Up @@ -47,12 +47,12 @@ class Susp
return f(this);
}
// We use it for debugging
bool isForced() const
{
bool isForced() const
{
// acquire barrier
auto f = _thunk.load(std::memory_order_acquire);
return f == &thunkGet;
}
return f == &thunkGet;
}
private:
// Atomic pointer to function with release/acquire semantics
mutable std::atomic<T const & (*)(Susp *)> _thunk;
Expand All @@ -70,21 +70,22 @@ template<class T>
class Cell
{
public:
Cell() {} // only to initialize _memo
Cell(T v, Stream<T> const & tail)
: _v(v), _tail(tail)
{}
T val() const
{
return _v;
}
Stream<T> pop_front() const
{
return _tail;
}
Cell() {} // only to initialize _memo
Cell(T v, Stream<T> const & tail)
: _v(v), _tail(tail)
{}
explicit Cell(T v) : _v(v) {}
T val() const
{
return _v;
}
Stream<T> pop_front() const
{
return _tail;
}
private:
T _v;
Stream<T> _tail;
T _v;
Stream<T> _tail;
};

// CellFun is a function object that creates a Cell
Expand All @@ -97,12 +98,12 @@ class CellFun
CellFun(T v, Stream<T> const & s) : _v(v), _s(s) {}
explicit CellFun(T v) : _v(v) {}

Cell<T> operator()()
{
return Cell<T>(_v, _s);
}
T _v;
Stream<T> _s;
Cell<T> operator()()
{
return Cell<T>(_v, _s);
}
T _v;
Stream<T> _s;
};

// Stream is either empty
Expand All @@ -112,9 +113,9 @@ template<class T>
class Stream
{
private:
std::shared_ptr <Susp<Cell<T>>> _lazyCell;
std::shared_ptr <Susp<Cell<T>>> _lazyCell;
public:
Stream() {}
Stream() {}
explicit Stream(T v)
{
auto f = CellFun<T>(v);
Expand All @@ -126,8 +127,8 @@ class Stream
_lazyCell = std::make_shared<Susp<Cell<T>>>(f);
}
Stream(std::function<Cell<T>()> f)
: _lazyCell(std::make_shared<Susp<Cell<T>>>(f))
{}
: _lazyCell(std::make_shared<Susp<Cell<T>>>(f))
{}
Stream(Stream && stm)
: _lazyCell(std::move(stm._lazyCell))
{}
Expand All @@ -137,78 +138,76 @@ class Stream
return *this;
}
bool isEmpty() const
{
return !_lazyCell;
}
T get() const
{
return _lazyCell->get().val();
}
Stream<T> pop_front() const
{
return _lazyCell->get().pop_front();
}
{
return !_lazyCell;
}
T get() const
{
return _lazyCell->get().val();
}
Stream<T> pop_front() const
{
return _lazyCell->get().pop_front();
}
// for debugging only
bool isForced() const
{
return !isEmpty() && _lazyCell->isForced();
}
bool isForced() const
{
return !isEmpty() && _lazyCell->isForced();
}
// Lazy take
Stream take(int n) const
{
if (n == 0 || isEmpty())
return Stream();
auto cell = _lazyCell;
return Stream([cell, n]()
{
auto v = cell->get().val();
auto t = cell->get().pop_front();
return Cell<T>(v, t.take(n - 1));
});
}
Stream drop(int n) const
{
if (n == 0)
return *this;
if (isEmpty())
return Stream();
auto t = pop_front();
return t.drop(n - 1);
}
Stream take(int n) const
{
if (n == 0 || isEmpty())
return Stream();
auto cell = _lazyCell;
return Stream([cell, n]()
{
auto v = cell->get().val();
auto t = cell->get().pop_front();
return Cell<T>(v, t.take(n - 1));
});
}
Stream drop(int n) const
{
if (n == 0)
return *this;
if (isEmpty())
return Stream();
auto t = pop_front();
return t.drop(n - 1);
}
// Lazy reverse
Stream reverse() const
{
return rev(Stream());
}
Stream reverse() const
{
return rev(Stream());
}
private:
Stream rev(Stream acc) const
{
if (isEmpty())
return acc;
auto v = get();
auto t = pop_front();
Stream nextAcc([=]
{
return Cell<T>(v, acc);
});
return t.rev(nextAcc);
}
Stream rev(Stream acc) const
{
if (isEmpty())
return acc;
auto v = get();
auto t = pop_front();
Stream nextAcc([=]
{
return Cell<T>(v, acc);
});
return t.rev(nextAcc);
}
};

// Lazy concatentation of two streams

template<class T>
Stream<T> concat( Stream<T> const & lft
, Stream<T> const & rgt)
Stream<T> concat( Stream<T> lft
, Stream<T> rgt)
{
if (lft.isEmpty())
return rgt;
return Stream<T>([=]()
{
T val = lft.get();
auto tail = lft.pop_front();
return Cell<T>(val, concat<T>(tail, rgt));
});
if (lft.isEmpty())
return rgt;
return Stream<T>([=]()
{
return Cell<T>(lft.get(), concat<T>(lft.pop_front(), rgt));
});
}

template<class T, class F>
Expand All @@ -228,36 +227,36 @@ template<class T>
class Queue
{
public:
Queue() : _lenF(0), _lenR(0) {}
Queue(int lf, Stream<T> f, int lr, Stream<T> r)
: _lenF(lf), _front(f), _lenR(lr), _rear(r)
{}
bool isEmpty() const { return _lenF == 0; }
Queue push_back(T x) const
{
return check(_lenF, _front, _lenR + 1, Stream<T>(x, _rear));
}
T front() const { return _front.get(); }
Queue pop_front() const
{
return check(_lenF - 1, _front.pop_front(), _lenR, _rear);
}
// for debugging only
int lenF() const { return _lenF; }
int lenR() const { return _lenR; }
Stream<T> const & fStream() const { return _front; }
Stream<T> const & rStream() const { return _rear; }
Queue() : _lenF(0), _lenR(0) {}
Queue(int lf, Stream<T> f, int lr, Stream<T> r)
: _lenF(lf), _front(f), _lenR(lr), _rear(r)
{}
bool isEmpty() const { return _lenF == 0; }
Queue push_back(T x) const
{
return check(_lenF, _front, _lenR + 1, Stream<T>(x, _rear));
}
T front() const { return _front.get(); }
Queue pop_front() const
{
return check(_lenF - 1, _front.pop_front(), _lenR, _rear);
}
// for debugging only
int lenF() const { return _lenF; }
int lenR() const { return _lenR; }
Stream<T> const & fStream() const { return _front; }
Stream<T> const & rStream() const { return _rear; }
private:
static Queue check(int lf, Stream<T> f, int lr, Stream<T> r)
{
if (lr <= lf) return Queue(lf, f, lr, r);
static Queue check(int lf, Stream<T> f, int lr, Stream<T> r)
{
if (lr <= lf) return Queue(lf, f, lr, r);
// Left stream is a lazy concatenation and reverse
return Queue(lf + lr, concat(f, r.reverse()), 0, Stream<T>());
}
return Queue(lf + lr, concat(f, r.reverse()), 0, Stream<T>());
}
private:
int _lenF;
Stream<T> _front;
int _lenR;
Stream<T> _rear;
int _lenF;
Stream<T> _front;
int _lenR;
Stream<T> _rear;
};
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