Expansion of TeX macros inside the Lua function

* Expansion of TeX macros inside the Lua function
@ 2010-08-01  9:45 Jaroslav Hajtmar
  2010-08-01 15:08 ` Hans Hagen
  0 siblings, 1 reply; 3+ messages in thread
From: Jaroslav Hajtmar @ 2010-08-01  9:45 UTC (permalink / raw)
  To: mailing list for ConTeXt users

I came across an interesting issue (for me), which is probably the 
beginner, but accompanied me for a long time. The problem is probably 
that I do not understand very well the principles of operation LuaTeX 
and while I want to do more complex things.

I think many beginners will love it when someone indicate solutions.

My problem is that I need in my complex application, evaluate parameters 
of Lua functions, which are a TeX macros (respectively their expanded 
contents). I did not discover the possibility of expansion of TeX 
macros, which is a parameter Lua function.

Here are three examples in which I demonstrate the problem.

1. In first example is function parameter a text string.

\ctxlua{pars('a,b,c,d,e')}

Everything works as expected - evaluation of parameter was carried out 
OK - comma separator was found and replaced.

2. In second example is a function parameter a TeX macro \printaction. 
Macro expanded before entering the function. Everything works as 
expected too - comma separator is found and replaced:

\ctxlua{pars('\printaction')}

3. The third example of my most interesting. Function parameter in 
example is a TeX macro \printaction which not expanded, respectively 
expanded only when I printing it to TeX. Parameter of function is string 
"\printaction" in which it is futile to look for a comma separator. 
Comma not be found, although the content of macro face that is so.

\ctxlua{pars('\\printaction')}

Is there a possibility for this case, as in some way to save to Lua 
variable content of macro (of course expanded)?
I note that this example is important for me and I would like there to 
be a Lua function (eg "expandtostring"), which expanded a TeX macro into 
variable until inside function Lua.

I hope the my example (with comments) will be comprehensible and I 
apologize if the solution is too trivial. I searched dozens of examples, 
but I come across something similar.

Thanx very much - Jaroslav

Here is example:

\startluacode

function pars(inppar)
strpar=tostring(inppar) -- here I need a function "expandtostring(inppar)"
gsubstr=string.gsub(strpar, ',', ';')
tex.print("Input parametr (string or macro):  ")
tex.write(inppar)
tex.print("\\par")
tex.print("Content of string (macro): "..strpar) -- There will always be 
expansion
tex.print("\\par")
tex.print("Length string (macro):  "..string.len(inppar).."\\par")
tex.print("Length of content :  "..string.len(strpar).."\\par")
tex.print("Occurrence of the commma separator:  "..gsubstr.."\\par")
end

\stopluacode

\def\printaction{x,y,z}

\starttext

Example 1)

Function parameter in first example is a text string. Everything works as
expected - comma separator is found and replaced:

\ctxlua{pars('a,b,c,d,e')}

\blank[big]

Example 2)

Function parameter in second example is a TeX macro \backslash printaction
which expanded before entering the function. Everything works as 
expected too - comma separator is found
and replaced:

\ctxlua{pars('\printaction')}

\blank[big]

Example 3)

The third example of my most interesting. Function parameter in example is
a TeX macro \backslash printaction which not expanded, respectively 
expanded
only when I printing it to TeX. Parameter of function is still string
"\backslash printaction" in which it is futile to look for a comma 
separator.
Comma not be found, although the content of macro face that is so. Is 
there a
possibility for this case, as in some way to save to Lua variable 
content of
macro (of course expanded)?

\ctxlua{pars('\\printaction')}

\stoptext

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