complex_number.test

<<< native
[ EIdentifier "c"
, ESymbol Rel "="
, EOver
    False
    (EOver
       False
       (EGrouped
          [ EUnder
              False
              (EUnder False (EIdentifier "a") (ESymbol TUnder "\9183"))
              (EText TextNormal "real")
          , ESymbol Bin "+"
          , EUnder
              False
              (EUnder
                 False
                 (EGrouped
                    [ EIdentifier "b" , EStyled TextNormal [ EIdentifier "i" ] ])
                 (ESymbol TUnder "\9183"))
              (EText TextNormal "imaginary")
          ])
       (ESymbol TOver "\9182"))
    (EText TextNormal "complex number")
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mi>c</mi>
    <mo>=</mo>
    <mover>
      <mover>
        <mrow>
          <munder>
            <munder>
              <mi>a</mi>
              <mo accent="true">⏟</mo>
            </munder>
            <mtext mathvariant="normal">real</mtext>
          </munder>
          <mo>+</mo>
          <munder>
            <munder>
              <mrow>
                <mi>b</mi>
                <mi mathvariant="normal">i</mi>
              </mrow>
              <mo accent="true">⏟</mo>
            </munder>
            <mtext mathvariant="normal">imaginary</mtext>
          </munder>
        </mrow>
        <mo accent="true">⏞</mo>
      </mover>
      <mtext mathvariant="normal">complex number</mtext>
    </mover>
  </mrow>
</math>