Here’s my bit of public domain code for iterating through tables in Lua so that the elements are sorted. This routine works like the pairs() function included with Lua:

  -- Like pairs() but sorted
  function sPairs(inTable, sFunc)
    if not sFunc then
      sFunc = function(a, b)
        local ta = type(a)
        local tb = type(b)
        if(ta == tb)
          then return a < b 
        end
        return ta < tb
      end
    end
    local keyList = {}
    local index = 1
    for k,_ in pairs(inTable) do
      table.insert(keyList,k)
    end
    table.sort(keyList, sFunc)
    return function()
      key = keyList[index]
      index = index + 1
      return key, inTable[key]
    end
  end

Example usage of the above function:

  a={z=1,y=2,c=3,w=4}
  for k,v in sPairs(a) do
    print(k,v)
  end

With a sort function:

  a={z=1,y=2,c=3,w=4}
  function revS(a,b)
    return a>b
  end
  for k,v in sPairs(a,revS) do
    print(k,v)
  end

(Yes, this is a lot easier to do in Perl or Python, since those languages unlike Lua have built in list iterators, but it’s possible to do in Lua too)