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Diffstat (limited to 'src/library/scala/collection/GenTraversableOnce.scala')
| -rw-r--r-- | src/library/scala/collection/GenTraversableOnce.scala | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/src/library/scala/collection/GenTraversableOnce.scala b/src/library/scala/collection/GenTraversableOnce.scala index 244ff26397..4af2ca23be 100644 --- a/src/library/scala/collection/GenTraversableOnce.scala +++ b/src/library/scala/collection/GenTraversableOnce.scala @@ -67,6 +67,23 @@ trait GenTraversableOnce[+A] extends Any { */ def foreach[U](f: A => U): Unit + /** Tests whether this $coll is known to have a finite size. + * All strict collections are known to have finite size. For a non-strict + * collection such as `Stream`, the predicate returns `'''true'''` if all + * elements have been computed. It returns `'''false'''` if the stream is + * not yet evaluated to the end. Non-empty Iterators usually return + * `'''false'''` even if they were created from a collection with a known + * finite size. + * + * Note: many collection methods will not work on collections of infinite sizes. + * The typical failure mode is an infinite loop. These methods always attempt a + * traversal without checking first that `hasDefiniteSize` returns `'''true'''`. + * However, checking `hasDefiniteSize` can provide an assurance that size is + * well-defined and non-termination is not a concern. + * + * @return `'''true'''` if this collection is known to have finite size, + * `'''false'''` otherwise. + */ def hasDefiniteSize: Boolean def seq: TraversableOnce[A] @@ -81,6 +98,9 @@ trait GenTraversableOnce[+A] extends Any { /** Tests whether the $coll is empty. * + * Note: Implementations in subclasses that are not repeatedly traversable must take + * care not to consume any elements when `isEmpty` is called. + * * @return `true` if the $coll contains no elements, `false` otherwise. */ def isEmpty: Boolean |