Re: What does "\c!" means?

[Hans Hagen <pragma@wxs.nl>]

Wei-Wei Guo wrote:
> Hi Taco,
> 
> I just finished reading the 'System_Macros'. I still don't get the meaning
> of '\??pb @lang@' in the following codes:
> 
>   \def\lang#1%
>    {\def\biblanguage{#1}%
>     \ifcsname \??pb @lang@#1\endcsname
>         \expanded{\mainlanguage[\getvalue{\??pb @lang@#1}]}%
>         \expanded{\language[\getvalue{\??pb @lang@#1}]}%
>      \fi \ignorespaces}
> 
> In \lang[zh], for example, '\??pb @lang@' will be expanded to \@@pblangen,
> will it? Is \??pb a command? Is '\??pb @lang@' a command? Why can there be
> a whitespace in '\??pb @lang@'?

\??pb creates a namespace so you cannot mess with it in your document 
easily

\??pb is just a macro and the ?? makes it kind of private (hidden)

there has to be a whitespace otherwise you'd call for \??pb@lang@

> Sorry for some many questions. I'm so confused and don't know what to
> search in wiki, manuals, etc..

this is not stuff most users want to know or see; add a few 
\expandafter's, \futurelet's and \afterassignments and one wonders in 
what universe one has ended up

Hans

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