<<< mml $\begin{array}{ccc}1& \to & 2\\ \downarrow & x+\frac{2}{y^3}& \downarrow \\ 3& \to & 4\end{array}$ >>> native [ EArray [ AlignCenter , AlignCenter , AlignCenter ] [ [ [ ENumber "1" ] , [ ESymbol Accent "\8594" ] , [ ENumber "2" ] ] , [ [ ESymbol Rel "\8595" ] , [ EGrouped [ EIdentifier "x" , ESymbol Bin "+" , EFraction NormalFrac (ENumber "2") (ESuper (EIdentifier "y") (ENumber "3")) ] ] , [ ESymbol Rel "\8595" ] ] , [ [ ENumber "3" ] , [ ESymbol Accent "\8594" ] , [ ENumber "4" ] ] ] ]