I am trying to create a wrapper for the longtable environment and it works fine with the standard \newenvironment command. Now I want to use \NewDocumentEnvironment from the xparse package to allow more optional arguments. But the result looks different, there appears an additional cell below the table. Maybe it's caused by a linebreak from the \NewDocumentEnvironment command because the error doesn't appear when I move the \end{longtable} from the end-code-block to the start-code-block of the environment definition (like I did in the example in myxparsetable2 environment).

I created a minimal example. The error appears with myxparsetable1.



  \begin{longtable}{|c|c|c|} \hline%
    col1 & col2 & col3 \\ \hline%



  Normal longtable:
  \begin{longtable}{|c|c|c|} \hline
    col1 & col2 & col3 \\ \hline

  Custom mytable
  \begin{mytable}{|c|c|c|} \hline
      col1 & col2 & col3 \\ \hline

  Custom myxparsetable1
  \begin{myxparsetable1}{|c|c|c|} \hline
      col1 & col2 & col3 \\ \hline

  Custom myxparsetable2


And here is the output: Output from minimal example

  • 1
    It's a known problem: with \NewDocumentEnvironment{foo}, the macro \endfoo, that's internally used by LaTeX when \end{foo} is found, is \protected, so LaTeX starts a new row before realizing that the table should end. For the time being, use \newenvironment for environments involving tables. – egreg Jul 15 '14 at 14:13
  • Thanks for your fast and good answer. Do you know a way to use more than one optional argument with \newenvironment? Thanks Martin – Martin Jul 15 '14 at 14:15
  • 1
    I forgot to say “Welcome to TeX.SX”! – egreg Jul 15 '14 at 14:28

It's a known problem: with \NewDocumentEnvironment{foo}, the macro \endfoo, that's internally used by LaTeX when \end{foo} is processed is “protected” and, because of this, LaTeX can't see that the alignment is to be ended until it has already started a new row.

The situation is mostly similar to having \multicolumn not as the first item in a cell.

What can I offer, if you want to scan multiple arguments for \begin{foo}, a kludge:

  ...something with #2 and #3...
  • That works fine for me! Thank you very much for your help. – Martin Jul 15 '14 at 14:49

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