Planetdance Help gives an example of using isaspect in this way: 'isaspect(0, sun, moon, square, 5) = 1'. However, Query language does not find variable 'square' (nor 'conjunction' or 'opposition').
Conversely, it runs if in all caps as per AstroBasic help: 'isaspect(1, SUN, MOON, CONJUNCTION) = 0'. So this seems inconsistent with e.g. 'distance(sun,moon)<10'.