%%
%%  Ein Beispiel der DANTE-Edition
%%
%%  1. Auflage
%%
%%
%%  Copyright (C) 2013 Herbert Voss
%%
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%%
%%  See http://www.latex-project.org/lppl.txt for details.
%%
%%
%% ====
% Show page(s) 1
%%
%%
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{luacode,libertine}
\begin{luacode}
 local translate={c='ĉ', g='ĝ', h='ĥ', j='ĵ', s='ŝ', u='û'}
 local function get_char_token(char)
   return token.create(unicode.utf8.byte(char))
 end
 local function get_token_char(tok)
   return tok[1] == 11 and unicode.utf8.char(tok[2])
 end
 local circumflex_token = get_char_token("^")
 local function is_circumflex(tok)
   return tok[1] == circumflex_token[1] and tok[2] == circumflex_token[2]
      and tok[3] == circumflex_token[3]
 end
 local function in_math_mode()
   local n = tex.nest[tex.nest.ptr]
   return n.mode == 235 or n.mode == -235
 end
 local function texperanto()
   local t = token.get_next()
   if not in_math_mode() and is_circumflex(t) then
     local u = token.get_next()
     local c = get_token_char(u)
     if c then
       local d = translate[c]
       if d then return get_char_token(d) else return {t, u} end
     else return {t, u} end
   else   return t end
 end
 luatexbase.add_to_callback("token_filter", texperanto, "texperanto")
\end{luacode}
%StopShownPreambleCommands
\begin{document}
^c ^g ^h ^j ^s ^u $a^2+b^2=c^2$ und $a^c\le h^j$
\end{document}