# Where `code` is a string.
bf = (code) :
   tape = (0)
   tape_pos = 0
   brackets = ()
   i = -1
   while (++i < code length) :
      if (code(i) == ">"): if (++tape_pos == tape length): tape append(0)..
      elsif (code(i) == "<"): tape_pos--.
      elsif (code(i) == "+"): tape(tape_pos) = tape(tape_pos) + 1.
      elsif (code(i) == "-"): tape(tape_pos) = tape(tape_pos) - 1.
      elsif (code(i) == "."): tape(tape_pos) chr print.
      elsif (code(i) == ","): tape(tape_pos) = read at(0) ord.
      elsif (code(i) == "["): brackets push(i).
      elsif (code(i) == "]") :
         if (tape(tape_pos) == 0): brackets pop.
         else: i = brackets(-1).
      .
   .
.