Converting math from LaTeX to ConTeXt

[Brooks Moses <bmoses@stanford.edu>]

First, by way of introduction: I've been using LaTeX for about five years 
now, but am quite new to ConTeXt.  I'm a grad student in mechanical 
engineering, so my primary uses of ConTeXt in the near future are likely to 
be for my thesis and associated presentations, all of which will likely 
have lots of complicated equations in them.

After looking at what documentation is available for this, I think I have a 
fair handle on the basics of including math in ConTeXt.  However, I do have 
some questions about things beyond the basics that I use rather frequently, 
and I haven't been able to find useful answers in the documentation or the 
list archives.

To begin with, I have the following sets of definitions in my standard 
LaTeX preamble.  I know that \newcommand and \renewcommand are 
LaTeX-specific; what's the appropriate ConTeXt equivalent?  Also, do \hat, 
\vec, and \overline work as I would expect?  And is there a direct 
equivalent to \boldsymbol from the amsmath package?  (I need something that 
will handle both roman and greek letters.)

   \renewcommand{\vec}[1]{{\boldsymbol{#1}}}
   \renewcommand{\hatn}{\hat{\vec{n}}}
   \newcommand{\filter}[1]{\overline{#1}}

Also, many of these equations run over multiple lines using the macros from 
the amsmath package (the "split" environment in particular, but also the 
"align" environment), and I haven't been able to find much documentation on 
how to do this in ConTeXt.  For an example of the sorts of things I end up 
doing:

   \begin{equation}
   \begin{split}
   \lefteqn{
     \frac{\partial (\rho (\phi u)_j)}{\partial t}
        + \nabla_k (\rho (\phi u)_k u_j)
   }\quad\quad
   \\
   = &\;
     -\nabla_j (\phi p)
     + \nabla_j (\lambda \nabla_k (\phi u_k))
     + \nabla_k \left[\mu \left( \nabla_k (\phi u)_j
     + (\nabla_j (\phi u)_k) \right) \right]
   \\&\;
     {} - \lambda (\nabla_j u_k) \nabla_k \phi
     - \mu (\nabla_k \phi) \nabla_k u_j
     - \mu (\nabla_k u_k) \nabla \phi_j
     - \tau_{\text{surface, $jk$}} \nabla_k \phi
   \end{split}
   \end{equation}

Looking at that reminds me that I also rather heavily use the \text command 
from amsmath as well, and rely on its ability to properly size things in 
subscripts and such.  Does this (or an analogue) exist in ConTeXt?

Any suggestions?  I'd like to be able to simply cut and paste the equations 
like this one from my LaTeX documents into my ConTeXt documents with as 
little editing as possible (so that I can maintain consistency between 
documents in each format), but anything that produces the same output would 
be good to know about.

Thanks much!
- Brooks