########## better put this in private.bashlib
load_filter() {
# $1 .. filter status
# $2 .. compress flag
local funtag="[${FUNCNAME[0]}]"
	unset -f filter

	[[ -f filter            ]]  && mv filter filter.old
	[[ -f filter.compress   ]]  && rm -f filter.compress

	./mkfilter $1

	if [ -f filter.old ]
	then    diff -c filter filter.old > filter-diffs
	else    [[ -f filter-diffs ]] && rm -f filter-diffs
	fi

	# If the 'compress filter' flag is set then compress filter;
	# i.e. remove comments and  empty lines for runtime
	if [ ! -z "$2" ]
	then    trace "$funtag Using filter compressed"
		compress_filter
		. filter.compress
	else	trace "$funtag Using filter plain"
		. filter
	fi
}