).setAttribute("form", "prefix");
          document.getElementById("prefix_set_to_infix").setAttribute("form", "infix");
          document.documentElement.classList.remove("reftest-wait");
      });
    </script>
  </head>
  <body>
    <!-- Prefix and infix forms of "+" have different default spacing in
         the operator dictionary. -->
    <p>
      <math>
        <mn>1</mn><mo id="infix_attach_prefix">+</mo><mn>2</mn>
      </math>
    </p>
    <p>
      <math>
        <mo id="prefix_attach_infix">+