Collecting command arguments in a startstop environment

[Brooks Moses <bmoses@stanford.edu>]

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