[NTG-context] MPenvironment ignored for btex..etex (or should I use sometxt)?

29 Sep 2006

      I'm not sure what's going on here, but this file fails (2006.09.28
beta): [well I have a better idea now after writing out the whole email,
see the end...]

=================== 3.tex =================
\starttext
\startMPenvironment
\def\2{hello}
\stopMPenvironment

\startreusableMPgraphic{fig}
label(btex \2 etex, origin);
\stopreusableMPgraphic

\reuseMPgraphic{fig}

\stoptext
=========================================

The error is (from 3.log):

============== error snippet ===============
systems         : begin file 3 at line 1
color           : currentcolor (def) is not defined 
\openout7 = `3-mpgraph.mp'.

! Undefined control sequence.
<argument>  label(btex \2
                          etex, origin);
\writecheckedMPgraphic ...icfalse \edef \ascii {#1
                                                  }\convertcommand \ascii \t...

\startMPgraphic ...hic \writecheckedMPgraphic {#1}
                                                  \stopwritingMPgraphic 
\handlereusableMPgraphic ...phic #3\stopMPgraphic 
                                                  \doifobjectssupportedelse ...

\douseMPgraphic ...s [#1][#2]\getvalue {\@@MPG #1}
                                                  {}\elabelgroup 
<to be read again> 

l.10 \reuseMPgraphic{fig}

? R
etc.
============== error snippet ===============

But 3-mpgraph.mp (produced after giving 'R' to enter nonstopmode) looks
fine:

=============== 3-mpgraph.mp ================
<lots of stuff>
beginfig(1);
verbatimtex \global \loadfontfileoncetrue \def \2{hello}  etex;
label(btex  \2 etex
, origin);
;
endfig;
let end=mprunend;
end.
=============== 3-mpgraph.mp ================

It processes by hand fine:

$ mpost -mem=metafun 3-mpgraph
...
1 output file written: 3-mpgraph.1

(or by using the system(texmfstart ...) command in 3.log)

Oh, wait, if metapost is fine with the file but ConTeXt isn't, then the
error above must be from ConTeXt parsing the metapost code and seeing
the \2, then complaining.  So am I supposed to use the global option to
\startMPenvironment?  If it's needed in this case, I think it would be
needed in every case (ConTeXt would see all the metapost uses of the
definition).  Or is btex deprecated and I should use \sometxt (except in
loops)?  Or am I just confused?!

-Sanjoy

`A society of sheep must in time beget a government of wolves.'
   -- Bertrand de Jouvenal

[NTG-context] MPenvironment ignored for btex..etex (or should I use sometxt)?

Sanjoy Mahajan