mo1.test

<<< mml
<?xml version="1.0" encoding="UTF-8"?>

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mo>-</mo> 
    <mn>1</mn> 
  </mrow> </math>
>>> native
[ ESymbol Bin "-" , ENumber "1" ]