diff options
Diffstat (limited to 'src/library/scala/collection/Iterator.scala')
| -rw-r--r-- | src/library/scala/collection/Iterator.scala | 123 |
1 files changed, 98 insertions, 25 deletions
diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala index c9037eb3e3..e2c271145d 100644 --- a/src/library/scala/collection/Iterator.scala +++ b/src/library/scala/collection/Iterator.scala @@ -182,7 +182,7 @@ object Iterator { } } def hasNext = (current ne null) && (current.hasNext || advance()) - def next() = if (hasNext) current.next else Iterator.empty.next + def next() = if (hasNext) current.next() else Iterator.empty.next() override def ++[B >: A](that: => GenTraversableOnce[B]): Iterator[B] = new ConcatIterator(current, queue :+ (() => that.toIterator)) @@ -191,11 +191,55 @@ object Iterator { private[scala] final class JoinIterator[+A](lhs: Iterator[A], that: => GenTraversableOnce[A]) extends Iterator[A] { private[this] lazy val rhs: Iterator[A] = that.toIterator def hasNext = lhs.hasNext || rhs.hasNext - def next = if (lhs.hasNext) lhs.next else rhs.next + def next() = if (lhs.hasNext) lhs.next() else rhs.next() override def ++[B >: A](that: => GenTraversableOnce[B]) = new ConcatIterator(this, Vector(() => that.toIterator)) } + + /** Creates a delegating iterator capped by a limit count. Negative limit means unbounded. + * Lazily skip to start on first evaluation. Avoids daisy-chained iterators due to slicing. + */ + private[scala] final class SliceIterator[A](val underlying: Iterator[A], start: Int, limit: Int) extends AbstractIterator[A] { + private var remaining = limit + private var dropping = start + @inline private def unbounded = remaining < 0 + private def skip(): Unit = + while (dropping > 0) { + if (underlying.hasNext) { + underlying.next() + dropping -= 1 + } else + dropping = 0 + } + def hasNext = { skip(); remaining != 0 && underlying.hasNext } + def next() = { + skip() + if (remaining > 0) { + remaining -= 1 + underlying.next() + } + else if (unbounded) underlying.next() + else empty.next() + } + override protected def sliceIterator(from: Int, until: Int): Iterator[A] = { + val lo = from max 0 + def adjustedBound = + if (unbounded) -1 + else 0 max (remaining - lo) + val rest = + if (until < 0) adjustedBound // respect current bound, if any + else if (until <= lo) 0 // empty + else if (unbounded) until - lo // now finite + else adjustedBound min (until - lo) // keep lesser bound + if (rest == 0) empty + else { + dropping += lo + remaining = rest + this + } + } + } } import Iterator.empty @@ -307,11 +351,11 @@ trait Iterator[+A] extends TraversableOnce[A] { /** Selects first ''n'' values of this iterator. * * @param n the number of values to take - * @return an iterator producing only of the first `n` values of this iterator, or else the + * @return an iterator producing only the first `n` values of this iterator, or else the * whole iterator, if it produces fewer than `n` values. * @note Reuse: $consumesAndProducesIterator */ - def take(n: Int): Iterator[A] = slice(0, n) + def take(n: Int): Iterator[A] = sliceIterator(0, n max 0) /** Advances this iterator past the first ''n'' elements, or the length of the iterator, whichever is smaller. * @@ -332,29 +376,24 @@ trait Iterator[+A] extends TraversableOnce[A] { /** Creates an iterator returning an interval of the values produced by this iterator. * * @param from the index of the first element in this iterator which forms part of the slice. - * @param until the index of the first element following the slice. + * If negative, the slice starts at zero. + * @param until the index of the first element following the slice. If negative, the slice is empty. * @return an iterator which advances this iterator past the first `from` elements using `drop`, * and then takes `until - from` elements, using `take`. * @note Reuse: $consumesAndProducesIterator */ - def slice(from: Int, until: Int): Iterator[A] = { + def slice(from: Int, until: Int): Iterator[A] = sliceIterator(from, until max 0) + + /** Creates an optionally bounded slice, unbounded if `until` is negative. */ + protected def sliceIterator(from: Int, until: Int): Iterator[A] = { val lo = from max 0 - var toDrop = lo - while (toDrop > 0 && self.hasNext) { - self.next() - toDrop -= 1 - } + val rest = + if (until < 0) -1 // unbounded + else if (until <= lo) 0 // empty + else until - lo // finite - new AbstractIterator[A] { - private var remaining = until - lo - def hasNext = remaining > 0 && self.hasNext - def next(): A = - if (remaining > 0) { - remaining -= 1 - self.next() - } - else empty.next() - } + if (rest == 0) empty + else new Iterator.SliceIterator(this, lo, rest) } /** Creates a new iterator that maps all produced values of this iterator @@ -805,8 +844,25 @@ trait Iterator[+A] extends TraversableOnce[A] { * or -1 if such an element does not exist until the end of the iterator is reached. * @note Reuse: $consumesIterator */ - def indexWhere(p: A => Boolean): Int = { + def indexWhere(p: A => Boolean): Int = indexWhere(p, 0) + + /** Returns the index of the first produced value satisfying a predicate, or -1, after or at + * some start index. + * $mayNotTerminateInf + * + * @param p the predicate to test values + * @param from the start index + * @return the index `>= from` of the first produced value satisfying `p`, + * or -1 if such an element does not exist until the end of the iterator is reached. + * @note Reuse: $consumesIterator + */ + def indexWhere(p: A => Boolean, from: Int): Int = { var i = 0 + while (i < from && hasNext) { + next() + i += 1 + } + var found = false while (!found && hasNext) { if (p(next())) { @@ -827,8 +883,26 @@ trait Iterator[+A] extends TraversableOnce[A] { * or -1 if such an element does not exist until the end of the iterator is reached. * @note Reuse: $consumesIterator */ - def indexOf[B >: A](elem: B): Int = { + def indexOf[B >: A](elem: B): Int = indexOf(elem, 0) + + /** Returns the index of the first occurrence of the specified object in this iterable object + * after or at some start index. + * $mayNotTerminateInf + * + * @param elem element to search for. + * @param from the start index + * @return the index `>= from` of the first occurrence of `elem` in the values produced by this + * iterator, or -1 if such an element does not exist until the end of the iterator is + * reached. + * @note Reuse: $consumesIterator + */ + def indexOf[B >: A](elem: B, from: Int): Int = { var i = 0 + while (i < from && hasNext) { + next() + i += 1 + } + var found = false while (!found && hasNext) { if (next() == elem) { @@ -1147,9 +1221,8 @@ trait Iterator[+A] extends TraversableOnce[A] { * $willNotTerminateInf */ def copyToArray[B >: A](xs: Array[B], start: Int, len: Int): Unit = { - require(start >= 0 && (start < xs.length || xs.length == 0), s"start $start out of range ${xs.length}") var i = start - val end = start + math.min(len, xs.length - start) + val end = start + math.min(len, xs.length - start) while (i < end && hasNext) { xs(i) = next() i += 1 |