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author | Martin Odersky <odersky@gmail.com> | 2016-03-01 18:39:50 +0100 |
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committer | Martin Odersky <odersky@gmail.com> | 2016-03-09 12:06:03 +0100 |
commit | ff6c79d22a0f0142d204e97b027b29eb869f0188 (patch) | |
tree | bfa31248b8c62b47f1a1cf52c640c2828f2cb30d /src | |
parent | bdd8c35447aa92969abf1dbaf479b6995fdfb7f4 (diff) | |
download | dotty-ff6c79d22a0f0142d204e97b027b29eb869f0188.tar.gz dotty-ff6c79d22a0f0142d204e97b027b29eb869f0188.tar.bz2 dotty-ff6c79d22a0f0142d204e97b027b29eb869f0188.zip |
New collection strawman
Centered around views instead of iterators.
Diffstat (limited to 'src')
-rw-r--r-- | src/strawman/collections/CollectionStrawMan4.scala | 486 |
1 files changed, 486 insertions, 0 deletions
diff --git a/src/strawman/collections/CollectionStrawMan4.scala b/src/strawman/collections/CollectionStrawMan4.scala new file mode 100644 index 000000000..9159b1cfc --- /dev/null +++ b/src/strawman/collections/CollectionStrawMan4.scala @@ -0,0 +1,486 @@ +package strawman.collections + +import Predef.{augmentString => _, wrapString => _, _} +import scala.reflect.ClassTag + +/** A strawman architecture for new collections. It contains some + * example collection classes and methods with the intent to expose + * some key issues. It would be good to compare this to other + * implementations of the same functionality, to get an idea of the + * strengths and weaknesses of different collection architectures. + * + * For a test file, see tests/run/CollectionTests.scala. + */ +object CollectionStrawMan4 { + + /* ------------ Base Traits -------------------------------- */ + + /** Iterator can be used only once */ + trait IterableOnce[+A] { + def iterator: Iterator[A] + } + + /** Base trait for generic collections */ + trait Iterable[+A] extends IterableOnce[A] with FromIterable[Iterable] { + def iterator: Iterator[A] + def view: View[A] = View.fromIterator(iterator) + def knownLength: Int = -1 + } + + /** Base trait for instances that can construct a collection from an iterator */ + trait FromIterable[+C[X] <: Iterable[X]] { + def fromIterable[B](v: Iterable[B]): C[B] + } + + /** Base trait for companion objects of collections */ + trait IterableFactory[+C[X] <: Iterable[X]] extends FromIterable[C] { + def empty[X]: C[X] = fromIterable(View.Empty) + def apply[A](xs: A*): C[A] = fromIterable(View.Elems(xs: _*)) + } + + /** Base trait for sequence collections */ + trait Seq[+A] extends Iterable[A] with FromIterable[Seq] { + def apply(i: Int): A + def length: Int + } + + trait Builder[-A, +To] { + def +=(x: A): this.type + def ++=(xs: IterableOnce[A]): Unit = xs.iterator.foreach(+=) + def result: To + } + + /* ------------ Operations ----------------------------------- */ + + /** Operations returning types unrelated to current collection */ + trait Ops[A] extends Any { + def iterator: Iterator[A] + def foreach(f: A => Unit): Unit = iterator.foreach(f) + def foldLeft[B](z: B)(op: (B, A) => B): B = iterator.foldLeft(z)(op) + def foldRight[B](z: B)(op: (A, B) => B): B = iterator.foldRight(z)(op) + def indexWhere(p: A => Boolean): Int = iterator.indexWhere(p) + def isEmpty: Boolean = !iterator.hasNext + def head: A = iterator.next + } + + /** Transforms returning same collection type */ + trait MonoTransforms[A, Repr] extends Any { + protected def coll: Iterable[A] + protected def fromIterable(it: Iterable[A]): Repr + def filter(p: A => Boolean): Repr = fromIterable(View.Filter(coll, p)) + def partition(p: A => Boolean): (Repr, Repr) = { + val pn = View.Partition(coll, p) + (fromIterable(pn.left), fromIterable(pn.right)) + } + def drop(n: Int): Repr = fromIterable(View.Drop(coll, n)) + def to[C[X] <: Iterable[X]](fv: FromIterable[C]): C[A] = fv.fromIterable(coll) + } + + trait PolyTransforms[A, C[X]] extends Any { + protected def coll: Iterable[A] + protected def fromIterable[B](it: Iterable[B]): C[B] + def map[B](f: A => B): C[B] = fromIterable(View.Map(coll, f)) + def flatMap[B](f: A => IterableOnce[B]): C[B] = fromIterable(View.FlatMap(coll, f)) + def ++[B >: A](xs: IterableOnce[B]): C[B] = fromIterable(View.Concat(coll, xs)) + def zip[B](xs: IterableOnce[B]): C[(A, B)] = fromIterable(View.Zip(coll, xs)) + } + + /** Transforms that only apply to Seq */ + trait MonoTransformsOfSeqs[A, Repr] extends Any with MonoTransforms[A, Repr] { + def reverse: Repr = fromIterable(View.Reverse(coll)) + } + + /** Implementation of Ops for all generic collections */ + implicit class IterableOps[A](val c: Iterable[A]) + extends AnyVal with Ops[A] { + def iterator = c.iterator + } + + /** Implementation of MonoTransforms for all generic collections */ + implicit class IterableMonoTransforms[A, C[X] <: Iterable[X]](val c: Iterable[A] with FromIterable[C]) + extends AnyVal with MonoTransforms[A, C[A]] { + protected def coll = c + protected def fromIterable(it: Iterable[A]): C[A] = c.fromIterable(it) + } + + /** Implementation of PolyTransforms for all generic collections */ + implicit class IterablePolyTransforms[A, C[X] <: Iterable[X]](val c: Iterable[A] with FromIterable[C]) + extends AnyVal with PolyTransforms[A, C] { + protected def coll = c + protected def fromIterable[B](it: Iterable[B]): C[B] = c.fromIterable(it) + } + + /** Implementation of MonoTransformsForSeqs for all generic collections */ + implicit class SeqMonoTransforms[A, C[X] <: Seq[X]](val c: Seq[A] with FromIterable[C]) + extends AnyVal with MonoTransformsOfSeqs[A, C[A]] { + protected def coll = c + protected def fromIterable(it: Iterable[A]): C[A] = c.fromIterable(it) + } + + /* --------- Concrete collection types ------------------------------- */ + + /** Concrete collection type: List */ + sealed trait List[+A] extends Seq[A] with FromIterable[List] { self => + def isEmpty: Boolean + def head: A + def tail: List[A] + def iterator = new Iterator[A] { + private[this] var current = self + def hasNext = !current.isEmpty + def next = { val r = current.head; current = current.tail; r } + } + def fromIterable[B](c: Iterable[B]): List[B] = List.fromIterable(c) + def apply(i: Int): A = { + require(!isEmpty) + if (i == 0) head else tail.apply(i - 1) + } + def :::[B >: A](prefix: List[B]): List[B] = + if (prefix.isEmpty) this + else Cons(prefix.head, prefix.tail ::: this) + def length: Int = + if (isEmpty) 0 else 1 + tail.length + } + + case class Cons[+A](x: A, xs: List[A]) extends List[A] { + def isEmpty = false + def head = x + def tail = xs + } + + case object Nil extends List[Nothing] { + def isEmpty = true + def head = ??? + def tail = ??? + } + + object List extends IterableFactory[List] { + def fromIterator[B](it: Iterator[B]): List[B] = + if (it.hasNext) Cons(it.next, fromIterator(it)) else Nil + def fromIterable[B](c: Iterable[B]): List[B] = c match { + case View.Concat(xs, ys: Iterable[B]) => + fromIterable(xs) ::: fromIterable(ys) + case View.Drop(xs: List[B], n) => + var i = 0 + var ys = xs + while (i < n && !xs.isEmpty) { + ys = ys.tail + i += 1 + } + ys + case _ => fromIterator(c.iterator) + } + } + + /** Concrete collection type: ArrayBuffer */ + class ArrayBuffer[A] private (initElems: Array[AnyRef], initLength: Int) + extends Seq[A] with FromIterable[ArrayBuffer] with Builder[A, ArrayBuffer[A]] { + def this() = this(new Array[AnyRef](16), 0) + private var elems: Array[AnyRef] = initElems + private var start = 0 + private var end = initLength + def apply(n: Int) = elems(start + n).asInstanceOf[A] + def length = end - start + override def knownLength = length + override def view = new ArrayBufferView(elems, start, end) + def iterator = view.iterator + def fromIterable[B](it: Iterable[B]): ArrayBuffer[B] = + ArrayBuffer.fromIterable(it) + def +=(elem: A): this.type = { + if (end == elems.length) { + if (start > 0) { + Array.copy(elems, start, elems, 0, length) + end -= start + start = 0 + } + else { + val newelems = new Array[AnyRef](end * 2) + Array.copy(elems, 0, newelems, 0, end) + elems = newelems + } + } + elems(end) = elem.asInstanceOf[AnyRef] + end += 1 + this + } + def result = this + def trimStart(n: Int): Unit = start += (n max 0) + override def toString = s"ArrayBuffer(${elems.slice(start, end).mkString(", ")})" + } + + object ArrayBuffer extends IterableFactory[ArrayBuffer] { + def fromIterable[B](c: Iterable[B]): ArrayBuffer[B] = c match { + case View.Concat(fst: ArrayBuffer[B], snd: ArrayBuffer[B]) => + val elems = new Array[AnyRef](fst.length + snd.length) + Array.copy(fst.elems, fst.start, elems, 0, fst.length) + Array.copy(snd.elems, snd.start, elems, fst.length, snd.length) + new ArrayBuffer(elems, elems.length) + case pd @ View.Partitioned(partition: View.Partition[B]) => + partition.distribute(new ArrayBuffer[B]()) + pd.forced.get.asInstanceOf[ArrayBuffer[B]] + case c if c.knownLength >= 0 => + val elems = new Array[AnyRef](c.knownLength) + val it = c.iterator + for (i <- 0 until elems.length) elems(i) = it.next().asInstanceOf[AnyRef] + new ArrayBuffer[B](elems, elems.length) + case _ => + val buf = new ArrayBuffer[B] + val it = c.iterator + while (it.hasNext) buf += it.next() + buf + } + } + + class ArrayBufferView[A](val elems: Array[AnyRef], val start: Int, val end: Int) extends RandomAccessView[A] { + def apply(n: Int) = elems(start + n).asInstanceOf[A] + } + + case class StringView(s: String) extends RandomAccessView[Char] { + val start = 0 + val end = s.length + def apply(n: Int) = s.charAt(n) + } + + /** Concrete collection type: String */ + implicit class StringOps(val s: String) extends AnyVal with Ops[Char] { + def iterator: Iterator[Char] = new StringView(s).iterator + } + + implicit class StringMonoTransforms(val s: String) + extends AnyVal with MonoTransformsOfSeqs[Char, String] { + protected def coll: Iterable[Char] = StringView(s) + protected def fromIterable(it: Iterable[Char]): String = { + val sb = new StringBuilder + for (ch <- it) sb.append(ch) + sb.toString + } + } + + implicit class StringPolyTransforms(val s: String) + extends AnyVal with PolyTransforms[Char, Seq] { + protected def coll = StringView(s) + protected def fromIterable[B](it: Iterable[B]): Seq[B] = List.fromIterable(it) + def map(f: Char => Char): String = { + val sb = new StringBuilder + for (ch <- s) sb.append(f(ch)) + sb.toString + } + def flatMap(f: Char => String) = { + val sb = new StringBuilder + for (ch <- s) sb.append(f(ch)) + sb.toString + } + def ++(xs: IterableOnce[Char]): String = { + val sb = new StringBuilder(s) + for (ch <- xs.iterator) sb.append(ch) + sb.toString + } + def ++(xs: String): String = s + xs + } + + /* ------------ Views --------------------------------------- */ + + /** A lazy iterable */ + trait View[+A] extends Iterable[A] with FromIterable[View] { + override def view = this + override def fromIterable[B](c: Iterable[B]) = c match { + case c: View[B] => c + case _ => View.fromIterator(c.iterator) + } + } + + /** Iterator defined in terms of indexing a range */ + trait RandomAccessView[+A] extends View[A] { + def start: Int + def end: Int + def apply(i: Int): A + def iterator: Iterator[A] = new Iterator[A] { + private var current = start + def hasNext = current < end + def next: A = { + val r = apply(current) + current += 1 + r + } + } + override def knownLength = end - start max 0 + } + + object View { + def fromIterator[A](it: => Iterator[A]): View[A] = new View[A] { + def iterator = it + } + case object Empty extends View[Nothing] { + def iterator = Iterator.empty + override def knownLength = 0 + } + case class Elems[A](xs: A*) extends View[A] { + def iterator = Iterator(xs: _*) + override def knownLength = xs.length + } + case class Filter[A](val underlying: Iterable[A], p: A => Boolean) extends View[A] { + def iterator = underlying.iterator.filter(p) + } + case class Partition[A](val underlying: Iterable[A], p: A => Boolean) { + val left, right = Partitioned(this) + def distribute(bf: => Builder[A, Iterable[A]]) = { + val lb, rb = bf + val it = underlying.iterator + while (it.hasNext) { + val x = it.next() + (if (p(x)) lb else rb) += x + } + left.forced = Some(lb.result) + right.forced = Some(rb.result) + } + } + case class Partitioned[A](partition: Partition[A]) extends View[A] { + private var myForced: Option[Iterable[A]] = None + def forced: Option[Iterable[A]] = myForced + private[View] def forced_=(x: Option[Iterable[A]]): Unit = myForced = x + def underlying = partition.underlying + def iterator = forced match { + case Some(c) => c.iterator + case None => + underlying.iterator.filter( + if (this eq partition.left) partition.p else !partition.p(_)) + } + } + case class Drop[A](underlying: Iterable[A], n: Int) extends View[A] { + def iterator = underlying.iterator.drop(n) + override def knownLength = + if (underlying.knownLength >= 0) underlying.knownLength - n max 0 else -1 + } + case class Map[A, B](underlying: Iterable[A], f: A => B) extends View[B] { + def iterator = underlying.iterator.map(f) + override def knownLength = underlying.knownLength + } + case class FlatMap[A, B](underlying: Iterable[A], f: A => IterableOnce[B]) extends View[B] { + def iterator = underlying.iterator.flatMap(f) + } + case class Concat[A](underlying: Iterable[A], other: IterableOnce[A]) extends View[A] { + def iterator = underlying.iterator ++ other + override def knownLength = other match { + case other: Iterable[_] if underlying.knownLength >= 0 && other.knownLength >= 0 => + underlying.knownLength + other.knownLength + case _ => + -1 + } + } + case class Zip[A, B](underlying: Iterable[A], other: IterableOnce[B]) extends View[(A, B)] { + def iterator = underlying.iterator.zip(other) + override def knownLength = other match { + case other: Iterable[_] if underlying.knownLength >= 0 && other.knownLength >= 0 => + underlying.knownLength min other.knownLength + case _ => + -1 + } + } + case class Reverse[A](underlying: Iterable[A]) extends View[A] { + def iterator = { + var xs: List[A] = Nil + val it = underlying.iterator + while (it.hasNext) xs = Cons(it.next(), xs) + xs.iterator + } + override def knownLength = underlying.knownLength + } + } + +/* ---------- Iterators ---------------------------------------------------*/ + + /** A core Iterator class */ + trait Iterator[+A] extends IterableOnce[A] { self => + def hasNext: Boolean + def next(): A + def iterator = this + def foldLeft[B](z: B)(op: (B, A) => B): B = + if (hasNext) foldLeft(op(z, next))(op) else z + def foldRight[B](z: B)(op: (A, B) => B): B = + if (hasNext) op(next(), foldRight(z)(op)) else z + def foreach(f: A => Unit): Unit = + while (hasNext) f(next()) + def indexWhere(p: A => Boolean): Int = { + var i = 0 + while (hasNext) { + if (p(next())) return i + i += 1 + } + -1 + } + def filter(p: A => Boolean): Iterator[A] = new Iterator[A] { + private var hd: A = _ + private var hdDefined: Boolean = false + + def hasNext: Boolean = hdDefined || { + do { + if (!self.hasNext) return false + hd = self.next() + } while (!p(hd)) + hdDefined = true + true + } + + def next() = + if (hasNext) { + hdDefined = false + hd + } + else Iterator.empty.next() + } + + def map[B](f: A => B): Iterator[B] = new Iterator[B] { + def hasNext = self.hasNext + def next() = f(self.next()) + } + + def flatMap[B](f: A => IterableOnce[B]): Iterator[B] = new Iterator[B] { + private var myCurrent: Iterator[B] = Iterator.empty + private def current = { + while (!myCurrent.hasNext && self.hasNext) + myCurrent = f(self.next()).iterator + myCurrent + } + def hasNext = current.hasNext + def next() = current.next() + } + def ++[B >: A](xs: IterableOnce[B]): Iterator[B] = new Iterator[B] { + private var myCurrent: Iterator[B] = self + private var first = true + private def current = { + if (!myCurrent.hasNext && first) { + myCurrent = xs.iterator + first = false + } + myCurrent + } + def hasNext = current.hasNext + def next() = current.next() + } + def drop(n: Int): Iterator[A] = { + var i = 0 + while (i < n && hasNext) { + next() + i += 1 + } + this + } + def zip[B](that: IterableOnce[B]): Iterator[(A, B)] = new Iterator[(A, B)] { + val thatIterator = that.iterator + def hasNext = self.hasNext && thatIterator.hasNext + def next() = (self.next(), thatIterator.next()) + } + } + + object Iterator { + val empty: Iterator[Nothing] = new Iterator[Nothing] { + def hasNext = false + def next = throw new NoSuchElementException("next on empty iterator") + } + def apply[A](xs: A*): Iterator[A] = new RandomAccessView[A] { + val start = 0 + val end = xs.length + def apply(n: Int) = xs(n) + }.iterator + } +} + |