<<< native [ ESubsup (EIdentifier "R") (ENumber "0") (ENumber "4") , ESymbol Rel "=" , ESubsup (EIdentifier "R") (EGrouped [ ENumber "0" , EPhantom (EIdentifier "fail") ]) (EGrouped [ ENumber "4" , EPhantom (EIdentifier "fail") ]) ] >>> eqn R sub 0 sup 4 = R sub {0 hphantom fail} sup {4 hphantom fail}