Compute the set difference between two objects.
# S4 method for Intervals_virtual,Intervals_virtual
interval_difference(x, y, check_valid = TRUE)An object representing the subset of the integers or real line, as
  determined by type(x), found in x but not in y.
An "Intervals" or "Intervals_full" object.
An "Intervals" or "Intervals_full" object, with a
    type slot matching that of x.
Should validObject be called on x and y
    before passing to compiled code? Also see
    interval_overlap.
These methods are just wrappers for
  interval_intersection and
  interval_complement.