% Implementacia \eqalignno v LaTeX2e.
% --------------------------------------------
% 28.12.2002
% --------------------------------------------
% V LaTeX2e je problem manualne cislovat
% rovnice v prostredi eqnarray. 
%
% V prostredi equation to az taky problem nie je, 
% staci % predefinovat
% {\renewcommand{\theequation}{P}
% \begin{equation} 1+1=2 \end{equation}}
%
% alebo aj
% $$1+1=2 \eqno{(\star)}$$
%
% Kedze som nenasiel ziadne zmysluplne LaTeXove riesenie,
% "ukradol" som definiciu plainTeXoveho prikazu
% \eqalignno, ktory sa chova velmi podobne.
\documentclass{article}
\usepackage{slovak}
\begin{document}

\makeatletter
% Toto je povodna plainTeXova definicia, ako je 
% uvedena v [TeXbook naruby] (P. Olsak)
%\def\eqalignno#1{\displ@y \tabskip=\centering
%\halign to\displaywidth{\hfil$\@lign\displaystyle{##}$%
%\tabskip=0pt &$\@lign\displaystyle{{}##}$\hfil
%\tabskip=\centering &\llap{$\@lign##$}\tabskip=0pt \crcr
%#1\crcr}}

%definicia z 'texmf\tex\latex\cjw\cjwplain.sty', Colin J. Wynne
%(balik Plain TeX Macros for LaTeX2e---CJW)
\def\eqalignno#1{\displ@y \tabskip\@centering
  \halign to\displaywidth{\hfil$\@lign\displaystyle{##}$%
  \tabskip\z@skip&$\@lign\displaystyle{{}##}$\hfil
  \tabskip\@centering &\llap{$\@lign##$}\tabskip\z@skip\crcr
    #1\crcr}} 
%
%priklad na pouzitie tohto balika
$$\eqalignno{a^2+b^2 &= c^2 & \rm[Py_1]\cr
c &= \sqrt{a^2+b^2} & \rm[Py_2]\cr}$$
\end{document}