On 09/08/2009, at 5:00 PM, Joseph Wright wrote:

> That leads to calls which look like:
>
> \DeclareDocumentCommand \foo { o m }
> \DeclareDocumentCommand \foo { o +m }
> \DeclareDocumentCommand \foo { O{default} m }
> \DeclareDocumentCommand \foo { d() l m }
> \DeclareDocumentCommand \foo { u{\bar} t+ +m }
> \DeclareDocumentCommand \foo { s D<>{default} b o +m }
>
> This does not seem too bad to me: what do other people think?

Comparing this back to the original xparse, the changes here are:

-  >{P} replaced by +
-  >{W} dropped, since it is applied automatically when necessary  
(final optional argument)
-  c dropped, replaced by 'd()'
-  d** and D**{} added
-  u* and U*{} added

Personally, I still prefer the simpler 'o'/'o{}' syntax, but if we  
feel that the disambiguation of 'o'/'O{}' is more straightforward I'm  
happy with your proposal above.

Regarding Lars' ideas in doc2l3, I do quite like the idea of his  
argument pre-processing stage. But let's discuss that afterwards. We  
can always add it with another letter!

Will