Re: Wrapping \type{}

[Hans Hagen <pragma@wxs.nl>]

At 01:20 30/05/2004, you wrote:
>In my BNF module I use " as an active character that begins and ends
>terminals in the grammar:
>
><regex>: <branch> ; <branch>, "\|", <regex>.
>
>Now, the above doesn't quite work as written, as \ is still active (and
>so is, in fact | as we're really inside a \starttabulate.
>
>What I would like for the "" pair to do is work as a wrapper for
>\type{}, so that everything in-between is passed on to \type{}.
>Is there a way of getting them to do that?
>
>This is my current definition:
>
>\gdef"%
>   {\ifBNFoutsidestring%
>     \global\BNFoutsidestringfalse%
>     \begingroup%
>       \BNFunsetcatcodes%
>       \catcode`\"\@@active%
>       \@@bnfterminalstart%
>   \else%
>       \@@bnfterminalstop%
>     \endgroup%
>     \global\BNFoutsidestringtrue%
>   \fi}
>
>I figured something like
>
>\long\gdef"#1"%
>   {\type{#1}}
>
>might work, but it didn't.  It chokes on "." where . is also an
>activated character for terminating a production in the grammar.
>
>Any suggestions on how to go about this?  I mean, the obvious solution
>is simply to write
>
><regex>: <branch> ; <branch>, "\type{\|}", <regex>.
>
>instead, but I would like to keep the input as clean as possible.
>         nikolai

\definestartstop[BNF][before=\startlines\setups{myBNF},after=\stoplines]

\startsetups[myBNF]
   \defineactivecharacter " 
{\bgroup\tttf\setupinlineverbatim\defineactivecharacter " {\egroup}}
   \defineactivecharacter < {\mathematics{\string<}}
   \defineactivecharacter > {\mathematics{\string>}}
\stopsetups

\starttext

\startBNF
<regex>: <branch> ; <branch>, "|", <regex>.
\stopBNF

\stoptext

(cross your fingers that this does not interfere with reading files, but 
normally < > " are taken care of)

an alternative is to write a plugin forthe verbatim environment (see 
verb-ini to get an idea of what nasty things are involved with catcode 
changes).

Hans