Hello!

Some days ago, I asked about how to use sans serifed font in all math
document. My approach, given those answers, was create a little function to
use the serif fonts in math (using \definestartstop) but, when there is
some align involved, it produces an error :-\ .

An example is the following:


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\definefontfamily     [mainface] [ss] [Latin Modern Sans]

\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:digitsnormal]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:digitsbold]

\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:uppercasenormal]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:uppercaseitalic]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:uppercasebold]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:uppercasebolditalic]

\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:lowercasenormal]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:lowercaseitalic]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:lowercasebold]
\definefallbackfamily [mainface] [mm] [Latin Modern Sans]
[preset=math:lowercasebolditalic]

\definefontfamily     [mainface] [mm] [Latin Modern Math]


\definestartstop
[formulass]
[
before={\startformula
\setupbodyfont[mainface]},
after=\stopformula
]


\starttext

    abcdefg ABCDEFG 123456 i

    \startformula
        {\tf abcdefg\,ABCDEFG} \quad abcdefg\,ABCDEFG \quad 123456 \quad
{\bf 123456}
    \stopformula

% it works:
\startformula
Y=X\beta+\varepsilon
\stopformula

% it works:
\startformulass
Y=X\beta+\varepsilon
\stopformulass

% it doesn't work:
\startformulass
\startalign[n=4]
\NC  Y_t \NC = \beta_0 \NC + \beta_1  x_t \NC + \varepsilon_t \NR
\NC  Y_t \NC = \beta_0 \NC + \beta_1  x_t \NC + \varepsilon_t \NR
\stopalign
\stopformulass


\stoptext
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


Could you please give me some advices?

Thanks in advance!


-- 
«...my role is to be on the bottom of things.»

Donald Knuth