使用階2.11.8 REPL爲desugar(印刷後壓片,取出<pressed TAB here>
):
scala> for (i <- 0 to 1; c <- "Hello") yield (i + c).toChar //print<pressed TAB here>
scala.Predef.intWrapper(0).to(1).flatMap[Char, scala.collection.immutable.IndexedSeq[Char]](((i: Int) =>
scala.Predef.augmentString(scala.Predef.augmentString("Hello").
map[Char, String](((c: Char) => i.+(c).toChar))(scala.Predef.StringCanBuildFrom))))(scala.collection.immutable.IndexedSeq.canBuildFrom[Char]) // : scala.collection.immutable.IndexedSeq[Char]
scala> for (i <- 0 to 1; c <- "Hello") yield (i + c).toChar //print
res4: scala.collection.immutable.IndexedSeq[Char] = Vector(H, e, l, l, o, I, f, m, m, p)
scala> for (c <- "Hello"; i <- 0 to 1) yield (i + c).toChar //print<pressed TAB here>
scala.Predef.augmentString("Hello").flatMap[Char, String](((c: Char) => scala.Predef.intWrapper(0).to(1).
map[Char, scala.collection.immutable.IndexedSeq[Char]](((i: Int) => i.+(c).toChar))(scala.collection.immutable.IndexedSeq.canBuildFrom[Char])))(scala.Predef.StringCanBuildFrom) // : String
scala> for (c <- "Hello"; i <- 0 to 1) yield (i + c).toChar //print
res5: String = HIeflmlmop
更可讀的輸出:
scala> (0 to 1).flatMap(i => "Hello".map(c => (i+c).toChar))
res14: scala.collection.immutable.IndexedSeq[Char] = Vector(H, e, l, l, o, I, f, m, m, p)
scala> "Hello".flatMap(c => (0 to 1).map(i => (i + c).toChar))
res15: String = HIeflmlmop
請參閱http://docs.scala-lang.org/tutorials/FAQ/yield.html –
簡而言之,在for-comprehensions中,返回類型由第一個集合或可穿越)使用。 –