Minimal debugger written in Ruby

debugger.rb

class Foo
  def speak
    'hello'
  end
end

my_proc = Proc.new do |event, file, line, id, binding, classname|
  printf "%8s %s:%-2d %10s %8s\n", event, file, line, id, classname
  while cmd = gets.chomp do
    if cmd == 'n'
      break
    elsif cmd == 'c'
      set_trace_func(nil)
    else
      begin
        p eval(cmd, binding)
      rescue Exception => e
        puts e.message
      end
    end
  end
end

def debugger
  set_trace_func(my_proc)
end

debugger

Foo.new.speak