Hello,
given is the following PlainTeX file:
%&luatex
% \message{\the\currentgrouplevel}
\directlua0{texio.write_nl(tex.currentgrouplevel)}
\bye
This results in:
This is LuaTeX, Version snapshot-0.29.0-2008072919 (Web2C 7.5.7)
(currentgrouplevel.tex
! You can't use `\currentgrouplevel' as tex library index.
l.3 ...lua0{texio.write_nl(tex.currentgrouplevel)}
?
Looking into section 4.1.1 of the manual, currentgrouplevel is not in
the list of tex's integer parameters -- unfortunately. It would be a
quite useful addition in order to create `grouped variables' in Lua
(variables whose previous value is restored at the end of a TeX
group):
-- Assume there are TeX two count registers allocated, `stackIndex'
-- and `groupIndex'
tex.count.stackIndex = 0
tex.count.groupLevel = -1
-- The `grouped variable' stack
local stack = { }
-- Sets a `grouped variable'
function set(name, value)
if tex.currentgrouplevel > tex.count.grouplevel then
-- New group opened since the last time. Create a new
stack
-- element
tex.count.stackIndex = tex.count.stackIndex + 1
stack[tex.count.stackIndex] = { }
tex.count.groupLevel = tex.currentgrouplevel
-- TODO: Optional: Clear the stack above the new element
to
-- release old values
end
-- Add the value
stack[tex.count.stackIndex][name] = value
end
-- Gets a `grouped variable'
function get(name)
-- Look through the stack, top to bottom
for i = tex.count.stackIndex, 1, -1 do
if stack[i][name] then
return stack[i][name]
end
end
-- Value not found
return nil
end
Jonathan
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