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 empty strings 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