diff options
| -rw-r--r-- | src/library/scala/collection/immutable/Stack.scala | 66 | ||||
| -rw-r--r-- | test/files/run/sequenceComparisons.scala | 2 |
2 files changed, 21 insertions, 47 deletions
diff --git a/src/library/scala/collection/immutable/Stack.scala b/src/library/scala/collection/immutable/Stack.scala index a49df4a0aa..a5d7e9515a 100644 --- a/src/library/scala/collection/immutable/Stack.scala +++ b/src/library/scala/collection/immutable/Stack.scala @@ -12,17 +12,19 @@ package scala.collection package immutable -import scala.annotation.tailrec +import generic._ +import mutable.{ ArrayBuffer, Builder } -object Stack { - val Empty: Stack[Nothing] = new Stack(Nil) - def apply[A](elems: A*) = new Stack(elems.toList) +object Stack extends SeqFactory[Stack] { + implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, Stack[A]] = new GenericCanBuildFrom[A] + def newBuilder[A]: Builder[A, Stack[A]] = new ArrayBuffer[A] mapResult (buf => new Stack(buf.toList)) + + @deprecated("Use Stack.empty instead") + val Empty: Stack[Nothing] = Stack() } /** This class implements immutable stacks using a list-based data - * structure. Instances of <code>Stack</code> represent - * empty stacks; they can be either created by calling the constructor - * directly, or by applying the function <code>Stack.Empty</code>. + * structure. * * @note This class exists only for historical reason and as an * analogue of mutable stacks @@ -33,7 +35,10 @@ object Stack { * @since 1 */ @serializable @SerialVersionUID(1976480595012942526L) -class Stack[+A] protected (protected val elems: List[A]) extends Seq[A] { +class Stack[+A] protected (protected val elems: List[A]) extends LinearSeq[A] + with GenericTraversableTemplate[A, Stack] + with LinearSeqLike[A, Stack[A]] { + override def companion: GenericCompanion[Stack] = Stack def this() = this(Nil) @@ -43,9 +48,8 @@ class Stack[+A] protected (protected val elems: List[A]) extends Seq[A] { */ override def isEmpty: Boolean = elems.isEmpty - /** The number of elements in the stack - */ - def length: Int = elems.length + override def head = elems.head + override def tail = new Stack(elems.tail) /** Push an element on the stack. * @@ -90,7 +94,7 @@ class Stack[+A] protected (protected val elems: List[A]) extends Seq[A] { * @return the top element. */ def top: A = - if (!elems.isEmpty) elems.head + if (!isEmpty) elems.head else throw new NoSuchElementException("top of empty stack") /** Removes the top element from the stack. @@ -100,31 +104,14 @@ class Stack[+A] protected (protected val elems: List[A]) extends Seq[A] { * @return the new stack without the former top element. */ def pop: Stack[A] = - if (!elems.isEmpty) new Stack(elems.tail) + if (!isEmpty) new Stack(elems.tail) else throw new NoSuchElementException("pop of empty stack") def pop2: (A, Stack[A]) = - if (!elems.isEmpty) (elems.head, new Stack(elems.tail)) + if (!isEmpty) (elems.head, new Stack(elems.tail)) else throw new NoSuchElementException("pop of empty stack") - /** Returns the n-th element of this stack. The bottom element has index - * 0, elements above are indexed with increasing numbers. - * - * @throws Predef.NoSuchElementException - * @param n the index number. - * @return the n-th element on the stack. - */ - def apply(n: Int): A = { - @tailrec - def walk(i: Int, xs: List[A]): A = - (i == 0, xs.isEmpty) match { - case (_, true) => throw new NoSuchElementException("index out of range") - case (true, _) => xs.head - case (false, _) => walk(i - 1, xs.tail) - } - - walk(n, elems) - } + override def reverse: Stack[A] = new Stack(elems.reverse) /** Returns an iterator over all elements on the stack. The iterator * issues elements in the reversed order they were inserted into the @@ -132,23 +119,10 @@ class Stack[+A] protected (protected val elems: List[A]) extends Seq[A] { * * @return an iterator over all stack elements. */ - override def iterator: Iterator[A] = new Iterator[A] { - private var cur = Stack.this - def hasNext: Boolean = !cur.isEmpty - def next: A = { val r = top; cur = cur.pop; r } - } - - /** Returns the hash code for this stack. - * - * @return the hash code of the stack. - */ - override def hashCode(): Int = //"Stack".hashCode - if (isEmpty) 0 - else pop2 match { case (x,y) => x.hashCode + y.hashCode } + override def iterator: Iterator[A] = elems.iterator /** Returns a string representation of this stack. */ override def toString() = elems.mkString("Stack(", ", ", ")") - } diff --git a/test/files/run/sequenceComparisons.scala b/test/files/run/sequenceComparisons.scala index e674d55bf7..2b5833aacc 100644 --- a/test/files/run/sequenceComparisons.scala +++ b/test/files/run/sequenceComparisons.scala @@ -22,7 +22,7 @@ object Test { // mutable.Queue(_: _*), immutable.Seq(_: _*), mutable.Seq(_: _*), - // immutable.Stack(_: _*), + immutable.Stack(_: _*), // mutable.Stack(_: _*), immutable.IndexedSeq(_: _*), // was Vector //mutable.Vector(_: _*), |