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 following function is an alternative which will omit empty strings from the returned table if a delimiter(s) is leading or trailing the string being exploded. This means it will return a more compact table in some cases where the input string has excessive delimiters. 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