; docformat = 'rst'

;+
; Returns the complement of an index array.
;
; :Returns:
;    lonarr or -1L if complement is empty
;
; :Params:
;    indices : in, required, type=lonarr
;       indices to complement
;    n : in, required, type=integer type
;       number of elements in full array
; 
; :Keywords:
;    count : out, optional, type=long
;       number of elements in the complement
;-
function mg_complement, indices, n, count=ncomplement
  compile_opt strictarr
  
  all = bytarr(n)
  all[indices] = 1B
  return, where(all eq 0B, ncomplement)
end