Lua实现split函数

function split(s, delim)
  if type(delim) ~= "string" or string.len(delim) = 0 then
    return
  end

  local start = 1
  local t = {}
  while true do
  local pos = string.find (s, delim, start, true) -- plain find
    if not pos then
     break
    end

    table.insert (t, string.sub (s, start, pos - 1))
    start = pos + string.len (delim)
  end
  table.insert (t, string.sub (s, start))

  return t
end