String exploding

This function adds the ability to explode strings in Lua.

function string.explode(str, div)
    assert(type(str) == "string" and type(div) == "string", "invalid arguments")
    local o = {}
    while true do
        local pos1,pos2 = str:find(div)
        if not pos1 then
            o[#o+1] = str
        o[#o+1],str = str:sub(1,pos1-1),str:sub(pos2+1)
    return o

Have an example:

tbl = string.explode("foo bar", " ")
print(tbl[1]) --> foo
-- since we added explode to the string table, we can also do this:
str = "foo bar"
tbl2 = str:explode(" ")
print(tbl2[2]) --> bar
-- to restore the original string, we can use Lua's table.concat:
original = table.concat(tbl, " ")
print(original) --> foo bar

The above function will potentially return a list peppered with empty strings if the original input string has leading, trailing or repeated delimiters. The following function is an alternative which will return a more compact table with these omitted. Due to these omissions, you won't be able to use table.concat to reverse it back into the original string.

function string.explode2(s, d)
  local t = {}
      local pos1, pos2 = string.find(s, d)
      t[#t + 1] = string.sub(s, 1, pos1 - 1)
      s = string.sub(s, pos2 + 1)
    until pos1 == nil
    if #s ~= 0 then t[#t+1] = s end
  return t