I have an HTML table with <td> elements that can span multiple rows:

<table border="1">
  <tbody>
    <tr>
      <th>A</th>
      <th>B</th>
      <th>C</th>
      <th>D</th>
    </tr>
    <tr>
      <th>1</th>
      <td rowspan="2">B12</td>
      <td>C1</td>
      <td rowspan="3">D123</td>
    </tr>
    <tr>
      <th>2</th>
      <td rowspan="2">C23</td>
    </tr>
    <tr>
      <th>3</th>
      <td>B3</td>
    </tr>
  </tbody>
</table>

And I would like to generate a tabular format from it:

A   B    C    D
A1  B12  C1   D123
A2  B12  C23  D123
A3  B3   C23  D123

I’m trying to do it with XPath 3.1 (I’m not against a XQuery or XSLT solution but I don’t think they can do any better here):

//table/tbody/(
    let
        $matx := map:merge((1 to count(tr)) ! map:entry(.,map{}))
    return
    tr/(
        let
            $x := position()
        return
        *[name() = "tr" or name() = "th"]/(
            let
                $str := string(),
                $pos := position(),
                $row := $matx($x),
                $y := ($pos to 1 + max(($pos, map:keys($row))))
                      => filter(function($i){ not(map:contains($row,$i)) })
                      => head()
            return
            ($x to $x + (if (@rowspan) then xs:integer(@rowspan) - 1 else 0))
            => fold-left($matx, function($m,$i) {
                $m => map:put($i, $m($i) => map:put($y, $str))
            })
        )
    )
)

The main problem is that I can’t update the global $matx while looping through the <tr>. I’m currently trying to refactor the code with fold-left but it’s become a real mess. I hope that there’s a simpler solution.