[Nikita S. Doroshenko]

I would like to check if this structure is exists and if it is - do nothing, else build this structure:

ADVANCED_INTERFACE_GLOBAL_CONSTANTS = {} -- root
ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS = {}  -- child of root
ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE = {}  -- child of child of  root
ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION = {}   -- child of child of child of root

Normally i use this code:

if not ADVANCED_INTERFACE_GLOBAL_CONSTANTS then
        ADVANCED_INTERFACE_GLOBAL_CONSTANTS = {}
    end
    if not ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS then
        ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS = {}
    end
    if not ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE then
        ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE = {}
    end
    if not ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION then
        ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION = nil
    end

But it's very long, and looks like "hardcodeing"
So I write this function:

function test(table)
    local orig
-- Lets split (table) string in to 4 strings: ADVANCED_INTERFACE_GLOBAL_CONSTANTS, STAMPS, ADVANCED_USER_INTERFACE, VERSION
    for token in string.gmatch(table, '([^.]+)') do
-- Then if first string is root (ADVANCED_INTERFACE_GLOBAL_CONSTANTS) we do nothing
        if orig == nil then
            orig = token
        else
-- Else, if it's not (ADVANCED_INTERFACE_GLOBAL_CONSTANTS) we concatenate strings in to (ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS), (ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE) and (ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION)
            orig = orig.."."..token
        end
-- Here we check if table exists - then do nothing - else we build our table or table in table...
        if not _G[token] or not _G[orig] then
-- PS. token always == ADVANCED_INTERFACE_GLOBAL_CONSTANTS
            print(orig)
--OUTPUT: 
--FIRST RUN: ADVANCED_INTERFACE_GLOBAL_CONSTANTS
--SECOND RUN: ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS
--THIRD RUN: ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE
--LAST RUN: ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION
            _G[orig] = {}
            print(_G[orig])
--OUTPUT: 
--FIRST RUN: table: 0x24425d0
--SECOND RUN: table: 0x24426c0
--THIRD RUN: table: 0x2442680
--LAST RUN: table: 0x2442860
        end
    end
end
 
test("ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION")
-- TESTING OUR test FUNCTION --
print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS)
--OUTPUT: table: 0x1e8ab20 (Correct table)
print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS)
--OUTPUT: nil (that mean table with STAMPS not exists :( )
print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE)
--OUTPUT: error: input: attempt to index a nil value (field 'STAMPS')
print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION)
--OUTPUT: error: input: attempt to index a nil value (field 'STAMPS')

Link to check this code: http://codepad.org/wGpAa1ph

The problem is that this function build strange tables and i can't print them or use them. Looks like if orig = ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS (with dot), then _G[orig] = {} not woring (tables are build inside function, but outside, it's broken)

print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS)
--OUTPUT: nil instead of nil. must be table
print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE)
--OUTPUT: error: input: attempt to index a nil value (field 'STAMPS')
print(ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE.VERSION)
--OUTPUT: error: input: attempt to index a nil value (field 'STAMPS')

Will very appreciate for help, or idea how I can fix this problem.