pluck

Lib.pluck : ('a -> bool) -> 'a list -> 'a * 'a list

Pull an element out of a list.

An invocation pluck P [x1,...,xk,...,xn] returns a pair (xk,[x1,...,xk-1,xk+1,...xn]), where xk has been lifted out of the list without disturbing the relative positions of the other elements. For this to happen, P xk must hold, and P xi must not have held for x1,...,xk-1.

Failure

If the input list is empty. Also fails if P holds of no member of the list. Also fails if an application of P fails.

Example

- val (x,rst) = pluck (fn x => x mod 2 = 0) [1,2,3];
> val x = 2 : int
  val rst = [1, 3] : int list

See also

Lib.first, Lib.filter, Lib.mapfilter, Lib.assoc1, Lib.assoc2, Lib.assoc, Lib.rev_assoc