My first and messy brainfuck interpreter written in ruby.

bf.rb

class Interpreter
  def initialize
    @stack = Array.new(30_000, 0)
    @loop_stack = Array.new
    @prog = ""
    @instruction_pointer = 0
    @data_pointer = 0
  end

  def load_file file_name
    @prog = open(file_name).readlines(chomp: true).join
  end

  def simple_exit_check = @instruction_pointer >= @prog.size

  def mov_data_pointer op
    if (@data_pointer - 1 < 0 && op == '<') || (@data_pointer + 1 >= @stack.size && op == '>')
      raise "Cannot move data pointer outside array bounds"
    else
      @data_pointer += op == '<' ? -1 : 1
    end
  end

  def incr_curr_byte = @stack[@data_pointer] = (@stack[@data_pointer] + 1) % 256
  def decr_curr_byte = @stack[@data_pointer] = (@stack[@data_pointer] - 1) % 256

  def output_curr_byte = print(@stack[@data_pointer].chr)
  def read_byte_and_store 
    input = gets[0]
    input = 10 if input == '\n'
    @stack[@data_pointer] = input == "4" ? 0 : input.ord
  end

  def exec_next_command
    op = @prog[@instruction_pointer]

    case op
    when '>'
      self.mov_data_pointer(op)
    when '<'
      self.mov_data_pointer(op)
    when '+'
      self.incr_curr_byte()
    when '-'
      self.decr_curr_byte()
    when '.'
      self.output_curr_byte()
    when ','
      self.read_byte_and_store()
    when '['
      if @stack[@data_pointer] == 0
        @instruction_pointer += 1 while @prog[@instruction_pointer] != ']'
        @instruction_pointer += 1
      else
        @loop_stack.push @instruction_pointer
      end
    when ']'
      @stack[@data_pointer] != 0 ? @instruction_pointer = @loop_stack.last : @loop_stack.pop
    end

    @instruction_pointer += 1
  end
end


i = Interpreter.new
print "Enter a bf filename: "
i.load_file(gets.chomp)
while not i.simple_exit_check()
  i.exec_next_command()
end