[NTG-context] Problem with Lua processing UTF8 substrings

1 Feb 2012

      Hello ConTeXist,

I want to use Lua to write characters (substrings) from a string, but I 
get an error message:

! String contains an invalid utf-8 sequence.

I tried various Lua functions for working with UTF8 strings for example:
string.subutf8(string, start[,end])
for i, char in str:nextutf8(orig_pos)
string.lenutf8(string),

but without success.

Can you please someone help?

Thanks
Jaroslav Hajtmar

Here is my minimal example:

\def\mymacro#1{\ctxlua{for i=1, string.len('#1') do 
context(string.sub('#1',i,i)..", ") end}}

\starttext

%\mymacro{šěřěžřýčřčžáýčý} % Here is a problem
\mymacro{asdfghjklqwertt} % Here is all OK

\stoptext