Re: common prefix?

[Scott Fial <scott@...>]

Perhaps I'm a bit late to the party, but here's my submission for 
computing the longest common prefix found in a list of strings:

function longest_common_prefix(t)
  local t1, n, byte = t[1] or "", #t, string.byte
  for i = 1, #t1 do
    local b = byte(t1, i)
    for j = 2, n do
      if byte(t[j], i) ~= b then return t1:sub(1, i - 1) end
    end
  end
  return t1
end

NOTE: It returns t[1] when #t == 1.  If you'd prefer that it return an 
empty string in that case, change line 2 to read:

  local t1, n, byte = #t > 1 and t[1] or "", #t, string.byte