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Assuming that the following assignments a = z.a etc. are correct, is it possible to use a function iso to obtain them. I thought of the name "iso" because in my main code a is a point, z.a is an affix that represents the point.

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{tkz-euclide}
\usepackage{tkz-elements}

\begin{document}
\parindent = 0pt
\begin{elements}
z.a   = {5,2}
z.b   = {3,-2}
z.c   = {4,0}


-- instead of a = z.a b = z.b c = z.c
__ is it possible to do iso() with
-- function iso ()
--      for i,k in pairs(z) do
--          ????
--       end
-- end
\end{elements}


\end{document}
Alain Matthes
  • 95,075
  • 1
    lua - Access local variable by name - Stack Overflow // access to global variables in lua - Stack Overflow – user202729 Mar 06 '23 at 14:04
  • as @user202729 just showed, it's sort of possible, but very weird and very fragile, what do you want to happen for keys with names that can't be used as variables, a' ? skip, give error, generate a variable you can not access? It will make the Lua very hard for any human to read as in all normal cases you can read the code statically to see where a variable is defined. It's possible to dynamcally alter the Lua symbol table, but not recommended for any normal use. – David Carlisle Mar 06 '23 at 14:32
  • @user202729 Too complicated and risky for a beginner like me with lua. I'm going to abandon this idea. – Alain Matthes Mar 06 '23 at 14:55
  • @DavidCarlisle I am not going to do anything special. My geometry figures are based on points given at the beginning. Only three or four points are involved. No a', then these are points that are used to construct other points with tools like the ones I have in tkz-euclide. I already have a hundred examples and as many lua functions et methods that allow me to recreate with lua all my old examples. I will test again to decide if I use this possibility (but by hand and without macro). – Alain Matthes Mar 06 '23 at 15:02
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    actually it's maybe not as bad as my orginal comment implied (I posted an answer) but it still seems scary, you can generate variables you can not access as variables, and can easily over-write anything – David Carlisle Mar 06 '23 at 15:06

1 Answers1

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You can access the global symbol table _G but I wouldn't recommend it here

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{luacode}
\begin{document}
\parindent = 0pt
\begin{luacode}
z={}
z.a   = {5,2}
z.b   = {3,-2}
z.c   = {4,0}
z["a'"] ={2,4}

-- instead of a = z.a b = z.b c = z.c


function iso ()
for i,k in pairs(z) do
 _G[i]=k
 end
end


iso()
\end{luacode}


% look at variable b


(\directlua{tex.print(b[1])},\directlua{tex.print(b[2])})


\end{document}
David Carlisle
  • 757,742
  • I saw _G from time to time in the documentations but I haven't studied it yet. If I understand correctly we have access to all global variables directly. Here the z table is global, can it be deleted by another program? – Alain Matthes Mar 06 '23 at 15:24
  • @AlainMatthes yes (but z being global is not used here, it makes a b c and a' global variables – David Carlisle Mar 06 '23 at 15:25
  • New problem !! is it possible to protect for example z? – Alain Matthes Mar 06 '23 at 16:01
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    @AlainMatthes no, a lua module is supposed to not use too much global namespace, if you only define tkz global variable as a table and all functions/variables are members of that module, it should not clash with others, but if you run the above and define a,b,c globally it is bound to clash – David Carlisle Mar 06 '23 at 16:10