newenvironment with markdown

[cdupont]

Hi, and thanks a lot for this package!
I'm trying to define a new environment with markdown:

\newenvironment{todo}
   {\begin{markdown}
   }
   { 
   \end{markdown}
   }

But I got this message:

Runaway argument?
! File ended while scanning use of ^^M.

[Witiko]

Hi. You cannot do that, since when the package encounters \begin{markdown}, it starts scanning for precisely the string \end{markdown} and there is no expansion during this procedure (similar to verbatim and other fragile environments). You can add support as follows:

\newenvironment{todo}
    \todoenv
    \relax

Given the following (slightly tricky) definition of \todoenv:

\begingroup
\catcode`\|=0\catcode`\<=1\catcode`\>=2%
\catcode`\\=12|catcode`|{=12|catcode`|}=12%
|gdef|todoenv<|markdownReadAndConvert<\end{todo}><|end<todo>>>
|endgroup

you can then just use

\begin{todo}
Hello, *world*!
\end{todo}

as you probably indended. This is very similar to how the markdown environment itself is defined in section 3.3.2 of the technical documentation.

[cdupont]

Thanks a lot.

[Witiko]

We may want to add support for easier use of the markdown LaTeX environment in other LaTeX environments using a similar approach as tabularx:

[Witiko]

@cdupont In commit 9be9a81 from PR #477, I added support for user-defined LaTeX environments with LaTeX markup: