Compilation error in LuaTeX, but in runs in Lua

I want to create an example for the extended Euclidean algorithm in LuaTeX.

documentclass[a4paper]{scrartcl}
usepackage{luacode}
usepackage{polyglossia}
setdefaultlanguage[spelling=new, babelshorthands=true]{german}

newcommand{wert}[1]{directlua{tex.sprint(#1)}}

begin{document}

begin{luacode*}
  function EEA(a,b)
    if b == 0 then return a, 1, 0 end
    d,s,t = EEA(b, a % b)
    x = s - (a//b) * t
    return d, t, x
  end
  p = 47
  q = 97
  d,x,y = EEA(p,q)
end{luacode*}
We have $wert{d} = wert{p} cdot wert{x} + wert{p} cdot wert{y}$.
end{document}

Running the code on https://www.lua.org/cgi-bin/demo works, but when I try LuaTeX, I get the error:

Language ngerman already loaded; id is 8[directlua]:4: unexpected symbol near
‘/’.
luacode@dbg@exec …code@maybe@printdbg {#1} #1 }

l.20 end{luacode*}

I thought i is connected with the percent sign, but

  function gcd(a,b)
    if b == 0 then return a end
    return gcd(b, a % b)
  end

works fine. How do I solve this?

I have LuaTeX version 1.0.4 and I just run lualatex lua_test.tex.