<<< native
[ EDelimited
    "("
    ")"
    [ Right
        (EArray
           [ AlignCenter , AlignCenter ]
           [ [ [ EGrouped [ ENumber "12" , EIdentifier "x" ] ]
             , [ ENumber "0" ]
             ]
           , [ [ ENumber "0" ] , [ ENumber "117" ] ]
           ])
    ]
]
>>> tex
\begin{pmatrix}
{12x} & 0 \\
0 & 117
\end{pmatrix}