stretchTable1.test

<<< 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" ]
      ]
    ]
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mtable>
    <mtr>
      <mtd columnalign="center" style="text-align: center">
        <mn>1</mn>
      </mtd>
      <mtd columnalign="center" style="text-align: center">
        <mo>→</mo>
      </mtd>
      <mtd columnalign="center" style="text-align: center">
        <mn>2</mn>
      </mtd>
    </mtr>
    <mtr>
      <mtd columnalign="center" style="text-align: center">
        <mo>↓</mo>
      </mtd>
      <mtd columnalign="center" style="text-align: center">
        <mrow>
          <mi>x</mi>
          <mo>+</mo>
          <mfrac>
            <mn>2</mn>
            <msup>
              <mi>y</mi>
              <mn>3</mn>
            </msup>
          </mfrac>
        </mrow>
      </mtd>
      <mtd columnalign="center" style="text-align: center">
        <mo>↓</mo>
      </mtd>
    </mtr>
    <mtr>
      <mtd columnalign="center" style="text-align: center">
        <mn>3</mn>
      </mtd>
      <mtd columnalign="center" style="text-align: center">
        <mo>→</mo>
      </mtd>
      <mtd columnalign="center" style="text-align: center">
        <mn>4</mn>
      </mtd>
    </mtr>
  </mtable>
</math>