Offtopic: TeX in MetaPost?

["Michal Kvasnička" <quasar@econ.muni.cz>]

Good evening.

I apologize that I dare to post here such offtopic, but I feel this is 
the right place to get an answer.
I try to write some general-purpose MetaPost macros for me with 
ConTeXt-like interface. For instance, I'd like something like this:
    label(point, "label=$A$, xlabel=$x_A$, ylabel=$y_A$, 
ylabelshift=left, lines=no, dotstyle=bigdot, ...");
I've done a lot of work and it almost works, but ... I failed to notice 
that TeX sequences are in normal cases included between btex ... etex 
and are preprocessed. In other words, they cannot be typeset as a 
string. I could use TEX macro, but it slows the process down in a 
horrible way.

I think the best way is this: In the first run of MetaPost to flush out 
all TeX codes, then process it with TeX (texexec), and then to include 
it in the second MetaPost run. But I don't know how to do it? Can you 
help me or at least hint where I could find an answer? And BTW, is this 
a good idea at all? Isn't there a better/faster way?

Many thanks for you kind help.
Michal Kvasnicka