table_to_string.lua

function tab2str(tab)
  local s = "{"
  for i,v in pairs(tab) do
    if type(v) == "table" then
      s = s.."{"
      for it,vt in pairs(v) do
        if type(vt) == "table" then
          s = s.."{"
          s = s..stringall.table(vt)
          if it ~= #v then
            s = s..","
          end
        elseif it ~= #v then
          if type(vt) == "string" then
            s = s..'"'..vt..'"'..","
          else
            s = s..tostring(vt)..","
          end
        else
          s = s..tostring(vt).."}"
        end
      end 
    elseif i ~= #tab then
      if type(v) == "string" then
         s = s..'"'..v..'"'..","
      else
        s = s..tostring(v)..","
      end
    elseif type(v) == "string" then
        s = s..'"'..v..'"'.."}"
    else
        s = s..tostring(v).."}"
    end
  end
  return s;
end

tab2str({1,2,{4,5,{6,7},"ab","cd"}}) will return {1,2,{4,5,{6,7},"ab","cd"}}