On 3/22/2021 9:40 AM, Petr Olsak wrote:
> The \suppressmathparerror=1 should suppress \par errors in math mode.
> OK, this works:
>
> -----------------
>
> \suppressmathparerror=1
> $$
> a
>
> b
> $$
> \bye
>
> ------------------
>
> but the following example gives error: Display math should end with
> \Ustopdisplaymath
>
> -------------------
>
> \suppressmathparerror=1
> $$
> \halign{#\cr a\cr}
>
> $$
> \bye
>
> -------------------
>
> The LuaTeX manual does not exactly describes the behavior of this case.
> So, I don't know if this is feature or bug.
>
> Note that the second example is primitive meaning of something like this:
>
> --------------------
>
> $$
> \eqalignno{...}
>
> $$
>
> --------------------
>
> If a user know that "empty lines are allowed in math mode" then he/she
> could leave empty line after \eqalignno too.

i'll check it