<<< native
[ EArray
    [ AlignCenter , AlignCenter , AlignCenter ]
    [ [ [ EGrouped
            [ EPhantom (EText TextNormal "fail")
            , EUnder
                False (EIdentifier "HT") (EPhantom (EText TextNormal "fail"))
            ]
        ]
      , [ ESymbol Rel "=" ]
      , [ EGrouped
            [ EOver
                False (EIdentifier "TH") (EPhantom (EText TextNormal "fail"))
            , EPhantom (EText TextNormal "fail")
            ]
        ]
      ]
    ]
]
>>> eqn
matrix{
ccol{ {hphantom {roman "fail"} HT from {hphantom {roman "fail"}}} }
ccol{ = }
ccol{ {TH to {hphantom {roman "fail"}} hphantom {roman "fail"}} }
}