Collecting command arguments in a startstop environment

Collecting command arguments in a startstop environment

[Brooks Moses]

There's a nice little problem that arises in LaTeX, of wanting to write a 
bit of code like the following, to define an environment that passes the 
contents of the environment to a command as an argument:

   \newcommand{\foo}[1]{...}
   \newenvironment{fooenv}{%
     \foo\bgroup
   }{%
     \egroup
   }

There's even a nice FAQ entry about this. [1]  As it turns out, the amsmath 
package defines a handy \collect@body command that handles collecting the 
environment body to pass it to a command.

Anyhow, I'm finding myself wanting to do this in ConTeXt, with of course 
replacing \newenvironment with \definestartstop.  Is there by any chance a 
built-in ConTeXt macro that can do this?  Or even things that would make a 
decent foundation for building such a thing?

Thanks much,
- Brooks


[1] http://www.tex.ac.uk/cgi-bin/texfaq2html?label=cmdasenv

Re: Collecting command arguments in a startstop environment

[Patrick Gundlach]

[...]

> Anyhow, I'm finding myself wanting to do this in ConTeXt, with of
> course replacing \newenvironment with \definestartstop. 

I didn't want to fiddle with \definestartstop, but here is a quick
hack:

--------------------------------------------------
\long\def\foo#1{ Hello #1!}
\long\def\startfoo #1 \stopfoo{\unskip \foo{#1}}

\starttext
\startfoo
World
\stopfoo
\startfoo
Brooks
\stopfoo
\startfoo
some

lines
\stopfoo
\stoptext
--------------------------------------------------

Patrick
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Re: Re: Collecting command arguments in a startstop environment

[Brooks Moses]

At 01:37 AM 8/2/2004, you wrote:
> > Anyhow, I'm finding myself wanting to do this in ConTeXt, with of
> > course replacing \newenvironment with \definestartstop.
>
>I didn't want to fiddle with \definestartstop, but here is a quick
>hack:
>
>--------------------------------------------------
>\long\def\foo#1{ Hello #1!}
>\long\def\startfoo #1 \stopfoo{\unskip \foo{#1}}
[...]

Oh, that's clever.  I'll have to ponder at whether it's got some drawbacks 
that mean it doesn't work for what I need, but it does seem promising.  Thanks!

- Brooks

Re: Collecting command arguments in a startstop environment

[Brooks Moses]

To answer my own question:

At 10:39 PM 8/1/2004, I wrote:
>There's a nice little problem that arises in LaTeX, of wanting to write a 
>bit of code like the following, to define an environment that passes the 
>contents of the environment to a command as an argument:
>
>   \newcommand{\foo}[1]{...}
>   \newenvironment{fooenv}{%
>     \foo\bgroup
>   }{%
>     \egroup
>   }
>
>There's even a nice FAQ entry about this. [1]  As it turns out, the 
>amsmath package defines a handy \collect@body command that handles 
>collecting the environment body to pass it to a command.
>
>Anyhow, I'm finding myself wanting to do this in ConTeXt, with of course 
>replacing \newenvironment with \definestartstop.  Is there by any chance a 
>built-in ConTeXt macro that can do this?  Or even things that would make a 
>decent foundation for building such a thing?

The \grabuntil and \processbetween commands, as defined in syst-ext.tex, do 
exactly what I'm asking for.

- Brooks

Re: Collecting command arguments in a startstop environment

[Hans Hagen Outside]

Brooks Moses wrote:

> To answer my own question:
>
> At 10:39 PM 8/1/2004, I wrote:
>
>> There's a nice little problem that arises in LaTeX, of wanting to 
>> write a bit of code like the following, to define an environment that 
>> passes the contents of the environment to a command as an argument:
>>
>>   \newcommand{\foo}[1]{...}
>>   \newenvironment{fooenv}{%
>>     \foo\bgroup
>>   }{%
>>     \egroup
>>   }
>>
>> There's even a nice FAQ entry about this. [1]  As it turns out, the 
>> amsmath package defines a handy \collect@body command that handles 
>> collecting the environment body to pass it to a command.
>>
>> Anyhow, I'm finding myself wanting to do this in ConTeXt, with of 
>> course replacing \newenvironment with \definestartstop.  Is there by 
>> any chance a built-in ConTeXt macro that can do this?  Or even things 
>> that would make a decent foundation for building such a thing?
>
>
> The \grabuntil and \processbetween commands, as defined in 
> syst-ext.tex, do exactly what I'm asking for.

If you want to play with low level features, it makes sense to look into:  

syst-gen.tex
syst-ext.tex 
(syst-new.tex)
supp-box.tex
supp-fun.tex

the interfaces of syst/supp modules are sort of 'public' and stable. These modules may also teach some tex tricks -) 
 
Hans 


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