Hi,

I defined some extra math symbols based on the help of David Munger.
David posted a question 2 years ago, asking the group how to define 
extra math symbols.
He found  a solution himself (see below) and what I am trying to do is 
to put this into a math collection like math-eul.tex
but I am not successfull.

I used his solution to define a module math-extra.tex based on 
math-eul.tex but I am getting errors like

! \textfont 14 is undefined (character).
\stopdisplaymath ->\stopinnermath $$
                                    \ifgridsnapping \egroup 
\afterdisplayspa...

\dostopformula ...eter \c!alternative \v!formula }
                                                  \resetlastlinewidth 
\nonoi...
l.18 \stopformula

I don't know what I am doing wrong, hope someone can help me
Attached my test files.

Kind regards

W. Neimeijer

David's solution

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\definebodyfont [28pt,24pt,18pt,
  17.3pt,14.4pt,12pt,11pt,10pt,9pt,8pt,7pt,6pt,5pt,4pt] [mm] [
  ex=txex sa 1,
  mc=txexa sa 1,
  mrbf=cmbx10 sa 1,
  exbf=cmex10  sa 1,
  mibf=cmmib10 sa 1,
  sybf=cmbsy10 sa 1,
  mabf=msam10  sa 1]
\setupbodyfont [12pt]

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% txfonts
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\definemathsymbol [oiint]               [op] [mc] ["08] [mc] ["09]
\definemathsymbol [oiiint]              [op] [mc] ["29] [mc] ["2a]
\definemathsymbol [ointctrclockwise]    [op] [mc] ["0A] [mc] ["0B]
\definemathsymbol [ointclockwise]       [op] [mc] ["0C] [mc] ["0D]
\definemathsymbol [varointctrclockwise] [op] [mc] ["2B] [mc] ["2C]
\definemathsymbol [varointclockwise]    [op] [mc] ["2D] [mc] ["2E]

\definemathsymbol [iint]                [op] [mc] ["21] [mc] ["22]
\definemathsymbol [iiint]               [op] [mc] ["23] [mc] ["24]
\definemathsymbol [iiiint]              [op] [mc] ["25] [mc] ["26]
\definemathsymbol [idotsint]            [op] [mc] ["27] [mc] ["28]

\definemathsymbol [oiintctrclockwise]   [op] [mc] ["40] [mc] ["41]
\definemathsymbol [oiintclockwise]      [op] [mc] ["48] [mc] ["49]
\definemathsymbol [varoiintctrclockwise][op] [mc] ["4A] [mc] ["4B]
\definemathsymbol [varoiintclockwise]   [op] [mc] ["42] [mc] ["43]

\definemathsymbol [oiiintctrclockwise]  [op] [mc] ["44] [mc] ["45]
\definemathsymbol [oiiintclockwise]     [op] [mc] ["4C] [mc] ["4D]
\definemathsymbol [varoiiintctrclockwise][op] [mc] ["4E] [mc] ["4F]
\definemathsymbol [varoiiintclockwise]  [op] [mc] ["46] [mc] ["47]


\starttext
The integral equation
\startformula
  \frac{d}{dt} \iiint_{\Omega} f \,dV
   = \iiint_{\Omega} Q \,dV
    - \oiint_{\partial\Omega} \vec J \cdot \vec{da}
\stopformula
can be written under the differential form
\startformula
  \frac{\partial f}{\partial t}
   = Q - \vec\nabla\cdot\vec J.
\stopformula

\stoptext

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%