在大于向量大小的索引处拆分

Question

为什么不这个表达式会抛出索引越界异常？

scala> Vector(1,2,3,4).splitAt(50000000)
res2: (Vector(1, 2, 3, 4),Vector())

Answer 1

来自splitAt的scaladoc：

/** Splits this $coll into two at a given position.
  *  Note: `c splitAt n` is equivalent to (but possibly more efficient than)
  *         `(c take n, c drop n)`.
  *  $orderDependent
  *
  *  @param n the position at which to split.
  *  @return  a pair of ${coll}s consisting of the first `n`
  *           elements of this $coll, and the other elements.
  */
def splitAt(n: Int): (Repr, Repr)

drop 的 Scaladoc：

/** Selects all elements except first ''n'' ones.
  *  $orderDependent
  *  @param  n    the number of elements to drop from this $coll.
  *  @return a $coll consisting of all elements of this $coll except the first `n` ones, or else the
  *          empty $coll, if this $coll has less than `n` elements.
  */
def drop(n: Int): Repr

对于take：

/** Selects first ''n'' elements.
  *  $orderDependent
  *  @param  n    the number of elements to take from this $coll.
  *  @return a $coll consisting only of the first `n` elements of this $coll,
  *          or else the whole $coll, if it has less than `n` elements.
  */
def take(n: Int): Repr

如您所见，这些方法旨在不引发任何异常。