Add parsing for double backslashes

[notjagan]

As of right now, the pegJS code does not handle double backslashes within LaTeX, which should act similar to carriage returns.

[physikerwelt]

@notjagan thank you for using github issues to record this problem

[HowardCohl]

Although this is a nice comment, I don't think this moves us any closer to a solution.

Apparently @ClaudeZou doesn't know how to fix this. Also, @notjagan doesn't know how to fix this.

@physikerwelt Do you have any ideas how to fix this?

[physikerwelt]

I don't think this moves us any closer to a solution

That's the next step.
First, we should be more formal and create a test case.
Please provide a test tuple with input, and expected output.

[notjagan]

Example input:
\frac12\\2

Expected output:
\frac{1}{2}\\2

Of course, at this point the pegJS code would also consume the whitespaces such as the newline in the expression, but as of now the issue is that it doesn't accept the double backslash. I will also create a test case for this in the all.js test cases once I add more test cases for parseSty.js.

[physikerwelt]

@notjagan Can you confim that the current results is S?

[physikerwelt]

Note, that you can parse for example

  \begin{pmatrix} 
    a_{11} & a_{12} & a_{13} \\ 
    a_{21} & a_{22} & a_{23} 
  \end{pmatrix} 

[physikerwelt]

@notjagan I have to admit that I do not really understand the example.
See the rendering of your example in standard latex.

[HowardCohl]

Here's another example

\begin{cases}
\dfrac{\gamma^2}{4m^2-1}, &  \mbox{$n-m$ even},
\\
- \dfrac{\gamma^2}{(2m-1)(2m-3)}, & \mbox{$n-m$ odd}.
\end{cases}

[notjagan]

@physikerwelt Running \frac12\\2 returns S, whereas \frac12 2 returns the expected output. Oddly enough, however, double backslashes do seem to work within pmatrices, so I'm not quite sure what's happening.

[physikerwelt]

@notjagan I think texvc works as expected. The grammar allows \\ where it does make sense
https://github.com/wikimedia/texvcjs/blob/master/lib/parser.pegjs#L300

[HowardCohl]

We have to fix cases in texvcjs.

Does it support for eqnarray?

[notjagan]

However, there are examples where the grammar does not allow \\ where it seems it should. I have recently been working in texer with KLSadd.tex, which contains usages of \\ that are not accepted by the grammar. For example, the math within

\begin{multline*}
F_4\left(a,b;b,b;\frac{-x}{(1-x)(1-y)},\frac{-y}{(1-x)(1-y)}\right)\\
=\left(\frac{(1-x)(1-y)}{1+xy}\right)^a\,
\hyp21{\thalf a,\thalf(a+1)}b{\frac{4xy}{(1+xy)^2}}.
\end{multline*}

is not accepted because of the double backslash.

[HowardCohl]

@physikerwelt In LaTeX, there are several ways to enter math mode, and depending on how you entered math mode, you get a different rendered output.

Such as \begin{multline}...\end{multline} vs. \begin{equation}...\end{equation}. If you are in {multline} environment, then \\ does something, but in {equation} environment, then it does nothing. So in this case, the \\ does make sense. So texvcjs should not fail.

[physikerwelt]

Historically $$ was used for rendering. Thus, you had to use a macro such
as \textstysle to get inline rendering.
However, we could add a parameter to pass the rendering mode to texvcjs.

On Aug 9, 2016 9:19 PM, "HowardCohl" notifications@github.com wrote:

@physikerwelt https://github.com/physikerwelt In LaTeX, there are
several ways to enter math mode, and depending on how you entered math
mode, you get a different rendered option.

Such as \begin{multline}...\end{multline} vs. \begin{equation}...\end{equation}.
If you are in {multline} environment, then \ does something, but in
{equation} environment, then it does nothing. So in this case, the \ does
make sense. So texvcjs should not fail.

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[notjagan]

@physikerwelt In texer, where I currently have a prototype of parsing text mode, I already have code that I can transfer over that can easily pass the rendering mode. However, I'm not sure where to accept the parameter nor how to parse the double backslashes. As I see it, the steps to completing this issue are as follows:

• Add parsing for double backslashes
• Add parameter for texvcjs to accept regarding rendering mode
• Pass parameter from external code into texvcjs (this step is only if text mode is implemented in this repository)