[NTG-context] How to make \def accept block or buffer as part of (long) command argument

[Hans Hagen]

On 1/2/2022 2:14 PM, Benjamin Buchmuller wrote:
> Thanks, Hans, for the answer, but I'm not sure if I get the point.
> 
> While this is possible in ConTeXt:
> 
> \startsection[title={My Title}]
> 
> \beginMyBlock
> bla bla
> \endMyBlock
> 
> \stopsection
> 
> The following won't work (end of file error):
> 
> \startMyCommand[optional={Maybe}]
> 
> \beginMyBlock
> bla bla
> \endMyBlock
> 
> \stopMyCommand
> 
> I had hoped for a simple command/modifier like \pleaseacceptblocks\def\startMyCommand[#1]#2\stopMyCommand  to have #2 work in a similar way.
> 
> But maybe, as Wolfgang stated here (https://www.mail-archive.com/ntg-context@ntg.nl/msg73956.html), buffers and blocks can't be used in commands. (To add: Even when passed as arguments during compilation?)

You can bet that WS is right.

You really have to go dirty tex for this kind of magic:

\defineblock[MyBlock]
\keepblocks[MyBlock]

\starttext

\tolerant\def\startMyCommand[#1]%
   {\begingroup
    \setcatcodetable\notcatcodes
    \dostartMyCommand[#1]}

\let\stopMyCommand\relax

\normalexpanded{\def\noexpand\dostartMyCommand[#1]#2\expandtoken\notcatcodes92 
stopMyCommand}%
   {\endgroup
    % whatever #1 does
    \setbuffer[foo]#2\endbuffer
    \typebuffer[foo]
    \getbuffer[foo]}

or

\normalexpanded{\def\noexpand\dostartMyCommand[#1]#2\retokenized\notcatcodes 
{\stopMyCommand}}%
   {\endgroup
    % whatever #1 does
    \setbuffer[foo]#2\endbuffer
    \typebuffer[foo]
    \getbuffer[foo]}

\startMyCommand[optional={Maybe}]

\beginMyBlock
bla bla
\endMyBlock

\stopMyCommand

\stoptext

and then of course further nesting mess ...

Hans

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