Support vertical lines in arrays

[jgm]

\begin{array}{rrr|r}
1 & 0 & 0 & x\\
0&1&0&b\\
0&0&1&c
\end{array}

Currently we get

\begin{array}{rrr|r}
                 ^
unexpected "|"
expecting letter, white space or "}"

It would be nice if we could represent these vertical lines. (This would require changing the EArray type.) Second best, perhaps the | could just be skipped?

[jgm]

MathJax produces this MathML, which works:

        <mtable columnalign="right right right right" rowspacing="4pt" 
columnspacing="1em" columnlines="none none solid"> 
          <mtr> 
...
          </mtr> 
        </mtable> 

[jgm]

Without the |, pandoc produces:

<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mtable>
    <mtr>
      <mtd columnalign="right">
        <mn>1</mn>
      </mtd>
      <mtd columnalign="right">
        <mn>0</mn>
      </mtd>
      <mtd columnalign="right">
        <mn>0</mn>
      </mtd>
      <mtd columnalign="right">
        <mi>x</mi>
      </mtd>
    </mtr>
    <mtr>
      <mtd columnalign="right">
        <mn>0</mn>
      </mtd>
      <mtd columnalign="right">
        <mn>1</mn>
      </mtd>
      <mtd columnalign="right">
        <mn>0</mn>
      </mtd>
      <mtd columnalign="right">
        <mi>b</mi>
      </mtd>
    </mtr>
    <mtr>
      <mtd columnalign="right">
        <mn>0</mn>
      </mtd>
      <mtd columnalign="right">
        <mn>0</mn>
      </mtd>
      <mtd columnalign="right">
        <mn>1</mn>
      </mtd>
      <mtd columnalign="right">
        <mi>c</mi>
      </mtd>
    </mtr>
  </mtable>
</math>

Obviously using the columnalign attribute on mtable is better. And if we represented the column lines, we could use columnlines as well.

[jgm]

I don't see anything corresponding to columnlines in OMML.

[aweinstock314]

I've written preliminary support for this at aweinstock314@15a2192 .

This currently fails most of the tests because it adds additional information to Text.TeXMath.Types.EArray; what's the procedure for updating the tests/ensuring that the additions are the only change?

[jgm]

make TESTARGS=--accept will update the tests with the current output.
We don't have a good system in place for ensuring that these changes are all sound, other than manual inspection -- sorry!

[aweinstock314]

I've updated the tests (and fixed a few bugs that looking at the ASTs revealed) in aweinstock314@c51c3fa .

Some of the tests already contain dashed/solid lines (e.g. mtableAlines1.mml, mlabeledtr1.mml), and the ASTs look right. They don't fully round trip because:

1. They use some additional MathML features (e.g. frame, rowlines) that aren't supported yet (which is orthogonal to this issue).
2. I expand the column separators to be equal to the number of columns minus one, and MathML treats a single-element columnlines as if it were repeated across the rows.

Should Writers.MathML re-compress columnlines (if they're all the same) to canonicalize?

[jgm]

MathML treats a single-element columnlines as if it were repeated across the rows.

Where is that documented? I couldn't find it on quick search.

[aweinstock314]

I manually opened tests/src/mlabeledtr1.mml (which uses columnlines="solid" despite having 3 columns) in firefox, and the output was consistent with that interpretation.

It's not explicitly spelled out by https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mtable#attr-columnlines (though the phrasing "Multiple values separated by space are allowed" seems a bit odd otherwise).

[aweinstock314]

Found the phrasing in the spec: "In this context, a single value specifies the value to be used for all rows (resp., columns or gaps)."

https://www.w3.org/TR/MathML3/chapter3.html#presm.mtable

[jgm]

Thanks. Yes, I think it would be best to collapse to the single value when they're all the same, if it's not too complicated to do it.

[aweinstock314]

aweinstock314@ed7259d

It emits compressed attributes (including emitting no attribute if the entire list is a copy of the default), and emits both "columnlines" and "columnalign" on the mtable instead of on the mtds.

Should I rebase this onto master and then submit it as a PR?

[jgm]

Should I rebase this onto master and then submit it as a PR?

Yes, please.