class IRB::ReadlineInputMethod

def self.initialize_readline 

def self.initialize_readline
  require "readline"
rescue LoadError
else
  include ::Readline
end

def encoding

The external encoding for standard input. 
def encoding
  @stdin.external_encoding
end

def eof?

See IO#eof? for more information.

if there is no more data to read.
Whether the end of this input method has been reached, returns +true+ 
def eof?
  @eof
end

def gets

See IO#gets for more information.

Reads the next line from this input method. 
def gets
  Readline.input = @stdin
  Readline.output = @stdout
  if l = readline(@prompt, false)
    HISTORY.push(l) if !l.empty?
    @line[@line_no += 1] = l + "\n"
  else
    @eof = true
    l
  end
end

def initialize

Creates a new input method object using Readline 
def initialize
  self.class.initialize_readline
  if Readline.respond_to?(:encoding_system_needs)
    IRB.__send__(:set_encoding, Readline.encoding_system_needs.name, override: false)
  end
  super
  @line_no = 0
  @line = []
  @eof = false
  @stdin = IO.open(STDIN.to_i, :external_encoding => IRB.conf[:LC_MESSAGES].encoding, :internal_encoding => "-")
  @stdout = IO.open(STDOUT.to_i, 'w', :external_encoding => IRB.conf[:LC_MESSAGES].encoding, :internal_encoding => "-")
  if Readline.respond_to?("basic_word_break_characters=")
    Readline.basic_word_break_characters = IRB::InputCompletor::BASIC_WORD_BREAK_CHARACTERS
  end
  Readline.completion_append_character = nil
  Readline.completion_proc = IRB::InputCompletor::CompletionProc
end

def inspect

For debug message 
def inspect
  readline_impl = (defined?(Reline) && Readline == Reline) ? 'Reline' : 'ext/readline'
  str = "ReadlineInputMethod with #{readline_impl} #{Readline::VERSION}"
  inputrc_path = File.expand_path(ENV['INPUTRC'] || '~/.inputrc')
  str += " and #{inputrc_path}" if File.exist?(inputrc_path)
  str
end

def line(line_no)

See IO#lineno for more information.

#line counts the number of times #gets is called.

Returns the current line number for #io. 
def line(line_no)
  @line[line_no]
end

def readable_after_eof?

See IO#eof for more information.

read.
Whether this input method is still readable when there is no more data to 
def readable_after_eof?
  true
end

def support_history_saving? 

def support_history_saving?
  true
end