def draw_staff(expr first, last, offset)=
+if test <> 0:
pickup pencircle scaled stafflinethickness;
for i:= first step 1 until last:
draw (- staff_space, (i + offset) * staff_space) .. (4 staff_space,( i+ offset)* staff_space);
endfor
- enddef;
+fi;
+
+enddef;
%