Remove an item from a list based on its index

Immutable list
list - object = new list without object

2010/2/12 Germán Ferrari <german.ferrari@gmail.com>

Hello.

I'm just not finding a direct way to remove an item from a list based on its index. I'm looking for something like this:

list.remove (index)

How do you do this in Scala?

Thank you.

Regards,
Germain.

Given that this operation is highly inefficient with lists (immutable ones, anyway), it does not exist.   def remove[T](list: List[T]) = {   val (start, _ :: end) = list.splitAt(index)   start ::: end }

On Fri, Feb 12, 2010 at 12:48 PM, Germán Ferrari <german.ferrari@gmail.com> wrote:

Hello.

I'm just not finding a direct way to remove an item from a list based on its index. I'm looking for something like this:

list.remove (index)

How do you do this in Scala?

Thank you.

Regards,
Germain.

--
Daniel C. Sobral

I travel to the future all the time.

On Fri, Feb 12, 2010 at 12:48:54PM -0200, Germán Ferrari wrote:
> I'm just not finding a direct way to remove an item from a list based
> on its index. I'm looking for something like this:
>
> list.remove (index)
>
> How do you do this in Scala?

If you're me you find yourself adding a method you keep needing. These
are in the pattern matcher somewhere.

/** Drops the 'i'th element of a list.
*/
def dropIndex[T](xs: List[T], n: Int) = {
val (l1, l2) = xs splitAt n
l1 ::: (l2 drop 1)
}

/** Extract the nth element of a list and return it and the remainder.
*/
def extractIndex[T](xs: List[T], n: Int): (T, List[T]) =
(xs(n), dropIndex(xs, n))