code: def transition(read, write, move)
        if read == @memory[@head]
          @memory[@head] = write
          case move
          when 'R'
            # Move right
            @memory << '@' if @memory[@head + 1]
            @head += 1
          when 'L'
            # Move left
            @memory.unshift('@') if @head == 0
            @head -= 1
          end
          return true
        else
          return false
        end
      end
docs: Creates a new tape.
  
   @param [String] string the input string
   Transitions the tape.
  
   @param [String] read the input symbol read
   @param [String] write the symbol to write
   @param [String] move Either 'L', 'R', or 'S' (default) to
     move left, right, or stay, respectively.
   @return [Boolean] whether the transition succeeded