Re: [NTG-context] Passing macro parameters to lua

5 Aug 2013


      On 8/5/2013 10:53 PM, Matt Gushee wrote:
...
Hello, good people--
I've encountered what appears to be a bug in either the TeX->Lua
interface or the documentation thereof (I have the latest stable
ConTeXt standalone from contextgarden.net).
I'm trying to create a macro that will insert different text depending
on whether one of the arguments is empty or not. My initial test
implementation (following the wiki section entitled "Passing arguments
and buffers: ConTeXt commands that hook into Lua") looked like this:
\startluacode
     userdata = userdata or {}
function userdata.empty_or_not(str)
         if str == "" or str == nil then
             context("{\\sc Empty}")
         else
             context(str)
         end
     end
\stopluacode
\def\emptyOrNot#1{%
     \ctxlua{userdata.empty_or_not(#1)}%
}
\starttext
\emptyOrNot{Amazing Text!}
\emptyOrNot{}
\stoptext
This did not work. I determined that even when I passed a non-empty
string, the Lua interpreter detected it as nil. It turns out the fix
was simple--I had to quote the string, as follows.
\def\emptyOrNot#1{%
     \ctxlua{userdata.empty_or_not("#1")}%
}
It took me a while to figure that out, though, since the wiki example
does not show quotes.
indeed you need quotes


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