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author | Daniel C. Sobral <dcsobral@gmail.com> | 2012-01-13 15:58:24 -0200 |
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committer | Daniel C. Sobral <dcsobral@gmail.com> | 2012-01-13 15:58:24 -0200 |
commit | 14138901500c0333ca199738cf80d2effde14279 (patch) | |
tree | 11abdf6917de648519009c755125e6a04ee0ae44 /src/library | |
parent | b0de5f13329aa24752fae079c50cc0584471379e (diff) | |
download | scala-14138901500c0333ca199738cf80d2effde14279.tar.gz scala-14138901500c0333ca199738cf80d2effde14279.tar.bz2 scala-14138901500c0333ca199738cf80d2effde14279.zip |
Improve description of flatten, flatMap
Add examples and better explain the expected return type of the
methods flatMap and flatten.
Closes SI-5371.
Diffstat (limited to 'src/library')
3 files changed, 38 insertions, 2 deletions
diff --git a/src/library/scala/collection/GenTraversableLike.scala b/src/library/scala/collection/GenTraversableLike.scala index 122eec2d90..c837775cf9 100644 --- a/src/library/scala/collection/GenTraversableLike.scala +++ b/src/library/scala/collection/GenTraversableLike.scala @@ -177,7 +177,28 @@ trait GenTraversableLike[+A, +Repr] extends GenTraversableOnce[A] with Paralleli def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That /** Builds a new collection by applying a function to all elements of this $coll - * and concatenating the results. + * and using the elements of the resulting collections. For example: + * + * {{{ + * def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+") + * }}} + * + * The type of the resulting collection is guided by the static type of $coll. This might + * cause unexpected results sometimes. For example: + * + * {{{ + * // lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set + * def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet) + * + * // lettersOf will return a Set[Char], not a Seq + * def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq) + * + * // xs will be a an Iterable[Int] + * val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2) + * + * // ys will be a Map[Int, Int] + * val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2) + * }}} * * @param f the function to apply to each element. * @tparam B the element type of the returned collection. diff --git a/src/library/scala/collection/TraversableLike.scala b/src/library/scala/collection/TraversableLike.scala index e2acc0b3e0..b4813e6341 100644 --- a/src/library/scala/collection/TraversableLike.scala +++ b/src/library/scala/collection/TraversableLike.scala @@ -709,6 +709,9 @@ trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] * outer $coll containing this `WithFilter` instance that satisfy * predicate `p` and concatenating the results. * + * The type of the resulting collection will be guided by the static type + * of the outer $coll. + * * @param f the function to apply to each element. * @tparam B the element type of the returned collection. * @tparam That $thatinfo diff --git a/src/library/scala/collection/generic/GenericTraversableTemplate.scala b/src/library/scala/collection/generic/GenericTraversableTemplate.scala index 12c1a75c7a..7333074778 100644 --- a/src/library/scala/collection/generic/GenericTraversableTemplate.scala +++ b/src/library/scala/collection/generic/GenericTraversableTemplate.scala @@ -116,7 +116,19 @@ trait GenericTraversableTemplate[+A, +CC[X] <: GenTraversable[X]] extends HasNew } /** Converts this $coll of traversable collections into - * a $coll in which all element collections are concatenated. + * a $coll formed by the elements of these traversable + * collections. + * + * The resulting collection's type will be guided by the + * static type of $coll. For example: + * + * {{{ + * val xs = List(Set(1, 2, 3), Set(1, 2, 3)) + * // xs == List(1, 2, 3, 1, 2, 3) + * + * val ys = Set(List(1, 2, 3), List(3, 2, 1)) + * // ys == Set(1, 2, 3) + * }}} * * @tparam B the type of the elements of each traversable collection. * @param asTraversable an implicit conversion which asserts that the element |