Brainf**k interpreter in Lua

bf-intp.lua

codes = ""; f = io.input(arg[1])
while true do
        c = io.read(); if c == nil then break end
        codes = codes..c
end

array = {}; p = 1; c = 1; cl = string.len(codes)
for i = 1, 65536 do array[i] = 0 end

while c <= cl do
        c0 = string.sub(codes, c, c)
        if     c0 == '+' then array[p] = array[p] + 1
        elseif c0 == '-' then array[p] = array[p] - 1
        elseif c0 == '>' then p = p + 1
        elseif c0 == '<' then p = p - 1
        elseif c0 == '.' then io.write(string.char(array[p]))
        elseif c0 == ',' then array[p] = tonumber(string.byte(io.read()))
        elseif c0 == '[' then
                if array[p] == 0 then
                        nest = 1
                        while nest ~= 0 do
                                c = c + 1
                                if string.sub(codes, c, c) == '[' then
                                        nest = nest + 1
                                end
                                if string.sub(codes, c, c) == ']' then
                                        nest = nest - 1
                                end
                        end
                end
        elseif c0 == ']' then
                if array[p] ~= 0 then
                        nest = 1
                        while nest ~= 0 do
                                c = c - 1
                                if string.sub(codes, c, c) == ']' then
                                        nest = nest + 1
                                end
                                if string.sub(codes, c, c) == '[' then
                                        nest = nest - 1
                                end
                        end
                end
        end
        c = c + 1
end