\altenv vs other \...env constructs

[josephwright]

If you look at beamer, in general \overlaything and overlaythingenv are related in that one can do

\overlaything<spec>{...}

and

\begin{overlaythingenv}<spec>
...
\end{overlaythingenv}

and they are basically the same.

That's not at all true for \alt vs altenv, where the latter has a lot of rather different arguments. I'm minded for the moment to skip altenv and if we need it to find a better name: thoughts?

[Skillmon]

I'm minded to skip all the environment variants... (I think I argued for this in the past)

[Skillmon]

More seriously, this doesn't look too difficult to do:

\NewDocumentEnvironment { altenv } { > { \@@_overlay_arg:n } D <> { all } m m m m }
  { \bool_if:NTF #1 { #2 } { #4 } }
  { \bool_if:NTF #1 { #3 } { #5 } }

So I'd just add it for the moment. If we later decide to rename or delete it that's easy to do.

[josephwright]

Indeed - implementation isn't really the issue :)