serialization nil values

[Markus Huber <pulse@...>]

I am writing a function to serialize values:

function Serialize.ToString(...)

Thank you very much Roberto for the chapter 12.1. PERSISTENCE.
But I don't like to name the variables at this stage and I prefer to
serialize variable arguments at once.

To accept also cycles I use the following system

a={[8]=10,20}
b=0
c=''
d=true
e=false

String=Serialize.ToString(a,b,c,d,e)
print(String)  --> local Table = {}
                   Table[1]={}
                   Table[1][1]=20
                   Table[1][8]=10
                   Table[2]=0
                   Table[3]=""
                   Table[4]=true
                   Table[5]=false
                   return unpack(Table)

The other side returns the perfect data:

Serialize.FromString(String)
   loadstring(String)()
end

So I can read at this point wich variables are expected:

local a,b,c,d,e = Serialize.FromString(String)

Works fine until now. But:

a={[8]=10,20}
b=nil         --> !
c=''
d=true
e=false

String=Serialize.ToString(a,b,c,d,e)
print(String)  --> local Table = {}
                   Table[1]={}
                   Table[1][1]=20
                   Table[1][8]=10
                   Table[2]=nil
                   Table[3]=""
                   Table[4]=true
                   Table[5]=false
                   return unpack(Table)

Returns only the variable a. Because unpack() can't know that I need
a return of a nil too. Table[2] is defined as nil and so doesn't exist
to unpack. Also c,d and e are missing.

>From the Lua documentation: "The number n of returned values is either
the value of Table.n, if it is a number, or one less the index of the
first absent (nil) value."

Any tips and ideas to solve this problem are welcome.

Possible: return unpack(),nil,unpack()  :-(
Or internal generated real variable names for each received argument?

   local _1[1]={}
         _1[1][1]=20
         _1[1][8]=10
   local _2[2]=nil
   local _3[3]=""
   local _4[4]=true
   local _5[5]=false
   return _1,_2,_3,_4,_5

Or what else?

Thank you.

--
Markus