Brainfuck.lua

local function brainFuck(data, input)
    local pos = 1
    local ptr = 0
    local lvl = 0

    local ram = {}
    local stack = {}

    local input = input or ""
    local result = ""
    local read = 1

    while pos <= #data do
        if ram[ptr] == nil then
            ram[ptr] = 0
        end

        local cmd = data:sub(pos, pos)
        local processed = true

        if cmd == '>' then
            ptr = ptr + 1
        elseif cmd == '<' then
            ptr = ptr - 1
        elseif cmd == '+' then
            ram[ptr] = ram[ptr] + 1
        elseif cmd == '-' then
            ram[ptr] = ram[ptr] - 1
        elseif cmd == '.' then
            local byte = ram[ptr]
            result = result .. string.char(byte)
        elseif cmd == ',' then
            local char = input:sub(read, read)
            ram[ptr] = char:byte()
            read = read + 1
        elseif cmd == '[' then
            if ram[ptr] > 0 then
                lvl = lvl + 1
                stack[lvl] = pos
            else
                pos = select(2, data:find("%b[]", pos))
            end
        elseif cmd == ']' then
            if ram[ptr] > 0 then
                pos = stack[lvl]
            else
                lvl = lvl - 1
            end
        end

        pos = pos + 1
    end

    print(result)
end