subtract : 'a list -> 'a list -> 'a list

SYNOPSIS
Computes the set-theoretic difference of two `sets'.

DESCRIPTION
subtract l1 l2 returns a list consisting of those elements of l1 that do not appear in l2. If both lists are initially free of repetitions, this can be considered a set difference operation.

FAILURE CONDITIONS
Never fails.

EXAMPLE
  # subtract [1;2;3] [3;5;4;1];;
  val it : int list = [2]
  # subtract [1;2;4;1] [4;5];;
  val it : int list = [1; 2; 1]

SEE ALSO
setify, set_equal, union, intersect.