function get_boolean_flags, nframes, idx
;	-------------------------------------------------------------
;+							12-Oct-95
;	Name: get_boolean_flags
;	PURPOSE:  convert a list of selected indices to a complete 
;		list of boolean flags.
;	Formal Parameters:
;		nframes		number of frames/flags
;		idx		list of selected frames 
;	Return: 
;		flist		a list of flags (nframes long) with 
;				true values for selected indices (idx)
;	History:
;		written 12-Oct-95, GAL
;-
;	------------------------------------------------------------

	list = indgen(nframes);		init frame numbers
	flist = list * 0;		init boolean flags for frames

	for i=0, n_elements(idx)-1 do begin
		flist(where(list eq idx(i))) = 1;	set true flags
	endfor

	return, flist;			return flags
	end