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Date:         Wed, 12 Aug 2009 23:45:02 +0200
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From: =?ISO-8859-1?Q?Lars_Hellstr=F6m?= <Lars.Hellstrom@RESIDENSET.NET>
Subject: Re: xparse
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
In-Reply-To:  <4A8318FB.5030507@morningstar2.co.uk>
Precedence: list
Status: R

Joseph Wright skrev:
> Lars Hellström wrote:
>> Since it was a while ago I'm not so sure, but I think I arrived at the
>> unified processor model only after I started coding. The seemingly less
>> complex idea of a separate processing stage turned out to be more
>> complex once you got down to do it.
> 
> This partly depends on your point of view! 

In this case, my point of view was that of _implementing_ an xparse 
with argument processing.

> In most cases,
> post-processing is not needed, so under any of the xparse-like
> implementations you end you with an arg spec. which doesn't look too
> intimidating:
> 
> { O{default} m o m }
> 
> or similar. I'd say that something like:
> 
> { >{ \preprocessora \preprocessorb }O{default} m o m }
> 
> is not too bad in comparison to
> 
> { @{ \preprocessora \preprocessorb O{default} }  @{} @{o} @{} }

For the record, the syntax I'd currently prefer (with one argspec per 
line, for clarity) for that is

   {
     @{ @{\preprocessorb} @{\preprocessora} O{default} }
     m
     o
     m
   }

It was *always* the intention that m, o, s, etc. should be available as 
argspecs! Back in 2008, I just /hadn't gotten around to/ do that in 
xdoc2l3, so I used the functionally equivalent @{}, @{o}, @{S{*}}, etc. 
in examples.

Lars Hellström