Salvete, I finally managed to make t-nath work with \eqalign and \eqalignno. (I assume I was not the only one having trouble there?) As it appears, nath gets really confused when subformulas are enclosed in {} and contain some form of delimiters. Therefore, the original definitions just don't work, but these modifications do, at least in some sense of “work”: \def\eqalignno#1% {\displ@y \tabskip\centering \vcenter{% \openup\jot\m@th \halign to \displaywidth {\hfil{\startnathdmath\@lign ##\stopnathdmath}\tabskip\z@skip &{\startnathdmath\@lign {}##\stopnathdmath}\hfil\tabskip\centering &\llap{$\@lign##$}\tabskip\z@skip\crcr #1\crcr}}} \def\eqalign#1% {\null \,% \vcenter {\openup \jot\m@th \ialign {\strut\hfil{\startnathdmath ##\stopnathdmath}&% {\startnathdmath {}##\stopnathdmath}\hfil\crcr #1\crcr}}% \,} And I've got another snippet I'd like to share, which helps displaying continued fractions in a linear format, using the “best” way of doing so I've met so far: \def\contfrac#1#2{% % To get the lines at the top right and bottom left % at the correct lengths, we need to know the final heights % of both top and bottom. Since styles ``C-up'' and ``C-down'' % are used only in generalized fractions, we need a trial % typesetting run for this. \begingroup \setbox\!!boxa\hbox{\trialtypesettingtrue\o@math\dcurrstyle@ {\setbox\nathbox\currstyle@hbox{%\vrule\!!depth .7\mex\!!width 0pt \botrestricted@false #1}% \!!dimena=\ht\nathbox \advance\!!dimena-\ht\sizebox@ \global\htdecrement@=\!!dimena % \!!dimena=\dp\nathbox \advance\!!dimena .5ex \dp\nathbox=\!!dimena \global\!!dimend=\dp\nathbox \box\nathbox \above\fracrulethickness@ \setbox\nathbox\currstyle@hbox{%\vrule\!!height 2\mex\!!width 0pt \toprestricted@false #2}% \!!dimenb=\dp\nathbox \advance\!!dimenb-\dp\sizebox@ \global\dpdecrement@=\!!dimenb % \!!dimenb=\ht\nathbox \advance\!!dimenb .5ex \ht\nathbox=\!!dimenb \global\!!dimene=\ht\nathbox \box\nathbox }% \o@math}% % % %% See the TeXbook, page 444 f., for what is happening here. \ifcase\mathcount@ \!!dimenf=\fontdimen8\textfont2 \!!dimeng=\fontdimen11\textfont2 \!!dimenh=3\fracrulethickness@ \!!dimeni=\fontdimen22\textfont2 \or \!!dimenf=\fontdimen9\scriptfont2 \!!dimeng=\fontdimen12\scriptfont2 \!!dimenh=\fracrulethickness@ \!!dimeni=\fontdimen22\scriptfont2 \else \!!dimenf=\fontdimen9\scriptscriptfont2 \!!dimeng=\fontdimen12\scriptscriptfont2 \!!dimenh=\fracrulethickness@ \!!dimeni=\fontdimen22\scriptscriptfont2 \fi % \!!dimenj=\dimexpr(\!!dimenf-\!!dimend)- (\!!dimeni+0.5\fracrulethickness@)\relax \ifdim\!!dimenj<\!!dimenh \advance\!!dimenf by \dimexpr(\!!dimenh-\!!dimenj)\relax \fi \!!dimenj=\dimexpr(\!!dimeni-0.5\fracrulethickness@)- (\!!dimene-\!!dimeng)\relax \ifdim\!!dimenj<\!!dimenh \advance\!!dimeng by \dimexpr(\!!dimenh-\!!dimenj)\relax \fi % \advance\!!dimenf by\dimexpr(-\!!dimeni)\relax \advance\!!dimeng by\dimexpr(+\!!dimeni)\relax % \setbox\!!boxa\hbox{% \o@math\dcurrstyle@ {\setbox\nathbox\currstyle@hbox{%\vrule\!!depth .7\mex\!!width 0pt \botrestricted@false #1}% \ifdim\ht\nathbox<1.6ex \ht\nathbox=1.6ex \fi \!!dimena=\ht\nathbox \advance\!!dimena-\ht\sizebox@ \global\htdecrement@=\!!dimena \setbox\!!boxb\hbox{% \vrule \!!depth\!!dimenf \!!height\ht\nathbox \!!width\fracrulethickness@ }% \dp\!!boxb=0pt \hfill\, \box\nathbox \,\hfill \hskip\fracrulethickness@\box\!!boxb \above\fracrulethickness@ \setbox\nathbox\currstyle@hbox{%\vrule\!!height 2\mex\!!width 0pt \toprestricted@false #2}% \ifdim\dp\nathbox<.4ex \dp\nathbox=.4ex \fi \!!dimenb=\dp\nathbox \advance\!!dimenb-\dp\sizebox@ \global\dpdecrement@=\!!dimenb \setbox\!!boxb\hbox{% \vrule \!!depth\dp\nathbox \!!height\!!dimeng \!!width\fracrulethickness@ }% \ht\!!boxb=0pt \box\!!boxb\hskip\fracrulethickness@ \hfill\, \box\nathbox \,\hfill }% \o@math}% \setbox\nathbox\copy\!!boxa \iftoprestricted@ \else \!!dimenb=\ht\nathbox \advance\!!dimenb .4\mex \ht\nathbox=\!!dimenb \fi \ifbotrestricted@ \else \!!dimenb=\dp\nathbox \advance\!!dimenb .5\mex \dp\nathbox=\!!dimenb \fi \box\nathbox % print \!!dimena=\ht\!!boxa \advance\!!dimena-\htdecrement@ \ht\!!boxa=\!!dimena \!!dimena=\dp\!!boxa \advance\!!dimena-\dpdecrement@ \dp\!!boxa=\!!dimena \global\setbox\sizebox@\copy\!!boxa \endgroup \resizebox@{\sizebox@}} I do assume the whole thing could be done with about half as many lines of code, but I was glad to finally understand how TeX typesets fractions and just ignored beautifying the code. Also note that the snippet uses \fracrulethickness@ from t-nath.tex, while I honestly consider using \fontdimen8\textfont3 or whichever font size is in use for the fraction. Well, work in progress. regards, Christopher Creutzig