[ruby-talk:00447] Re: interactive ruby, debugger

In message "[ruby-talk:00446] Re: interactive ruby, debugger"
    on 99/07/09, [e-mail] <[e-mail]> writes:
>> A ruby program `irb' (interactive ruby) is known. 
>
>I've been wondering why irb is not the built-in module ?

Well, well, all reason is no Engulish document is avairable.  Long
long ago in the ruby-dev, I said that I would translate README. But I
had not done it... Of cource, I did't have to translate because I'm
not the auther :-) However, So long as I said, I should do that. 

-- gotoken

# Now, it's


irb -- interactive ruby
				$Release Version: 0.5 $
			   	$Revision: 1.15 $
			   	$Date: 1999/03/05 05:18:07 $
			   	by Keiju ISHITSUKA(Nihon Rational Inc.)

1. What is irb?

irb stands for `interactive ruby'. irb is a tool to execute interactively
ruby expressions read from stdin. 

See also README-add for explaination of bundled commands/libraries. 



2. Invoking

% ruby -r irb -e0
% irb

Either of the aboves. In the former style, options can be specified
as follows:

% ruby -r irb -e0 -- -v



3. Usage

Use of irb is easy if you know ruby.  Executing irb, prompts are 
displayed as follows. Then, enter expression of ruby. A input is
executed when it is syntacticaly completed. 

dim% irb
irb(main):001:0> 1+2
3
irb(main):002:0> class Foo
irb(main):003:1>  def foo
irb(main):004:2>    print 1
irb(main):005:2>  end
irb(main):006:1> end
nil
irb(main):007:0> 

And, Readline extesion module can be used with irb. Using Readline
is the standard default action if Readline is installed. 



4. Command line option

  irb.rb [options] file_name opts
  options:
  -f		    suppress read ~/.irbrc 
  -m		    bc mode (fraction or matrix are available)
  -d                set $DEBUG  to true (same as `ruby -d')
  -r load-module    same as `ruby -r'
  --inspect	    uses `inspect' for output (the default except bc mode)
  --noinspect	    doesn't uses inspect for output
  --readline	    uses Readline extension module
  --noreadline	    doesn't use Readline extension module
  --prompt prompt-mode
  --prompt-mode prompt-mode
		    switches prompt mode. Pre-defined prompt modes are
		    `defalut', `simple', `xmp' and `inf-ruby'
			    
  --inf-ruby-mode   uses prompt appreciate for inf-ruby-mode on emacs. 
		    Suppresses --readline. 
  --simple-prompt   simple prompt mode
  --noprompt	    no prompt
  --tracer	    display trace for each execution of commands.
  --back-trace-limit n
		    displayes backtrace top n and tail n. The default
		    value is 16. 
  --irb_debug n	    sets internal debug level to n (It shouldn't be used)
  -v, --version	    prints the version of irb



5. Configurations

irb reads `~/.irbrc' when it is invoked. If `~/.irbrb' doesn't exist
irb try to read in the order `.irbrc', `irb.rc', `_irbrc' then `$irbrc'. 

The following is altanative to the command line option. To use them
type as follows in an irb session. 

IRB.conf[:IRB_NAME]="irb"
IRB.conf[:MATH_MODE]=false
IRB.conf[:USE_TRACER]=false
IRB.conf[:USE_LOADER]=false
IRB.conf[:IGNORE_SIGINT]=true
IRB.conf[:IGNORE_EOF]=false
IRB.conf[:INSPECT_MODE]=nil
IRB.conf[:IRB_RC] = nil
IRB.conf[:BACK_TRACE_LIMIT]=16
IRB.conf[:USE_LOADER] = false
IRB.conf[:USE_READLINE] = nil
IRB.conf[:USE_TRACER] = false
IRB.conf[:IGNORE_SIGINT] = true
IRB.conf[:IGNORE_EOF] = false
IRB.conf[:PROMPT_MODE] = :DEFALUT
IRB.conf[:PROMPT] = {...}
IRB.conf[:DEBUG_LEVEL]=0
IRB.conf[:VERBOSE]=true


5.1 Customizing prompt

To costomize the prompt you set a variable

IRB.conf[:PROMPT]

For example, describe as follows in `.irbrc'. 

IRB.conf[:PROMPT][:MY_PROMPT] = { # name of prompt mode
  :PROMPT_I => nil,		  # normal prompt
  :PROMPT_S => nil,		  # prompt for continuated strings
  :PROMPT_C => nil,		  # prompt for continuated statement
  :RETURN => "    ==>%s\n"	  # format to return value
}

Then, invoke irb with the above prompt mode by

% irb --prompt my-prompt

Or add the following in `.irbrc'. 

IRB.conf[:PROMPT_MODE] = :MY_PROMPT

Constants PROMPT_I, PROMPT_S and PROMPT_C specifies the format. 
In the prompt specification, some special strings are available. 

  %N	command name which is running
  %m	to_s of main object (self)
  %M	inspect of main object (self)
  %l	type 文字列中のタイプを表す(", ', /, ], `]'は%wの中の時)
  %NNi	indent level. NN is degits and means as same as printf("%NNd"). 
        It can be ommited
  %NNn	line number. 
  %%    %

For instance, the default prompt mode is defined as follows:

IRB.conf[:PROMPT_MODE][:DEFAULT] = {
      :PROMPT_I => "%N(%m):%03n:%i> ",
      :PROMPT_S => "%N(%m):%03n:%i%l ",
      :PROMPT_C => "%N(%m):%03n:%i* ",
      :RETURN => "%s\n"
} 

RETURN is used to printf. 


5.2 Configurating subirb

The command line option or IRB.conf specify the default behavior of
(sub)irb. On the other hand, each conf of in the next sction `6. Command' 
is used to individually configurate (sub)irb. 

If proc is set to IRB.conf[:IRB_RC], its subirb will be invoked after
execution of that proc under giving the context of irb as its
aregument. By this mechanism each subirb can be configurated. 



6. Command

For irb commands, both simple name and `irb_'-prefixed name are prepared. 

  exit, quit, irb_exit	
    Quits (sub)irb. 
    if you've done cb (see below), exit from the binding mode.

  conf, irb_context
    Displays current configuration. Modifing the configuration is
    achieved by sending message to `conf'. 

  conf.back_trace_limit
    Sets display lines of backtrace as top n and tail n. 
    The default value is 16.
    
  conf.debug_level = N
    Sets debug level of irb. 

  conf.ignore_eof = true/false
    Whether ^D (control-d) will be ignored or not. 
    If false is set, ^D means quit. 

  conf.ignore_sigint= true/false
    Whether ^C (control-c) will be ignored or not. 
    If false is set, ^D means quit.  If true, 
      during input:   cancel inputing then return to top level. 
      during execute: abondon current execution. 

  conf.inf_ruby_mode = true/false
    Whether inf-ruby-mode or not. The default value is false.

  conf.inspect_mode = true/false/nil
    Specifies inspect mode. 
    true:  display inspect
    false: display to_s
    nil:   inspect mode in non math mode, 
           non inspect mode in math mode. 

  conf.irb_level
    The level of cb. 

  conf.math_mode
    Whether bc mode or not. 

  conf.use_loader = true/false
    Whether irb's own file reader method is used when load/require or not. 
    This mode is globaly affected (irb wide). 

  conf.prompt_c
    prompt for a continuating statement (e.g, immediately after of `if')

  conf.prompt_i
    standard prompt

  conf.prompt_s
    prompt for a continuating string

  conf.rc
    Whether ~/.irbrc is read or not. 

  conf.use_prompt = true/false
    Prompting or not. 

  conf.use_readline = true/false/nil
    Whether readline is used or not. 
    true: uses 
    false: doen't use
    nil: intends to use readline except for inf-reuby-mode (default)

  conf.verbose=T/F
    Whether verbose messages are display or not. 

  cb, irb_change_binding [obj]
    Enter new binding which has a distinct scope of local variables. 
    If obj is given, obj will be self. 

  irb [obj]
    Invoke subirb. If obj is given, obj will be self. 

  jobs, irb_jobs
    List of subirb

  fg n, irb_fg n
    Switch into specified subirb. The following is candidates of n:

      irb number
      thhread
      irb object
      self(obj which is specified of irb obj)

  kill n, irb_kill n
    Kill subirb. The means of n is as same as the case of irb_fg. 



7. System variable

   _  The latest value of evaluation (it is local)


8. Session Example

dim% ruby irb.rb
irb(main):001:0> irb                        # invoke subirb
irb#1(main):001:0> jobs                     # list of subirbs
#0->irb on main (#<Thread:0x400fb7e4> : stop)
#1->irb#1 on main (#<Thread:0x40125d64> : running)
nil
irb#1(main):002:0> fg 0                     # switch job
nil
irb(main):002:0> class Foo;end
nil
irb(main):003:0> irb Foo                    # invoke subirb which has the 
                                            #              context of Foo
irb#2(Foo):001:0> def foo                   # define Foo#foo
irb#2(Foo):002:1>   print 1
irb#2(Foo):003:1> end
nil
irb#2(Foo):004:0> fg 0                      # switch job
nil
irb(main):004:0> jobs                       # list of job
#0->irb on main (#<Thread:0x400fb7e4> : running)
#1->irb#1 on main (#<Thread:0x40125d64> : stop)
#2->irb#2 on Foo (#<Thread:0x4011d54c> : stop)
nil
irb(main):005:0> Foo.instance_methods       # Foo#foo is defined asurely
["foo"]

irb(main):006:0> fg 2                       # switch job
nil
irb#2(Foo):005:0> def bar                   # define Foo#bar
irb#2(Foo):006:1>  print "bar"
irb#2(Foo):007:1> end
nil
irb#2(Foo):010:0>  Foo.instance_methods
["bar", "foo"]
irb#2(Foo):011:0> fg 0                      
nil
irb(main):007:0> f = Foo.new
#<Foo:0x4010af3c>
irb(main):008:0> irb f                      # invoke subirb which has the
                                            #  context of f (instance of Foo)
irb#3(#<Foo:0x4010af3c>):001:0> jobs
#0->irb on main (#<Thread:0x400fb7e4> : stop)
#1->irb#1 on main (#<Thread:0x40125d64> : stop)
#2->irb#2 on Foo (#<Thread:0x4011d54c> : stop)
#3->irb#3 on #<Foo:0x4010af3c> (#<Thread:0x4010a1e0> : running)
nil
irb#3(#<Foo:0x4010af3c>):002:0> foo         # evaluate f.foo
1nil
irb#3(#<Foo:0x4010af3c>):003:0> bar         # evaluate f.bar
barnil
irb#3(#<Foo:0x4010af3c>):004:0> kill 1, 2, 3# kill job
nil
irb(main):009:0> jobs
#0->irb on main (#<Thread:0x400fb7e4> : running)
nil
irb(main):010:0> exit                       # exit
dim% 


9. Restrictions

Because irb evaluates the inputs immediately after the imput is
syntactically completed, irb gives slight different result than
directly use ruby. Known difference is pointed out here. 


9.1 Here-document

Here-document is not avairable.  Though irb recognizes here-document, 
eval of ruby doesn't support here-document. 


9.2 Declaration of the local variable

The following causes an error in ruby:

eval "foo = 0"
foo
--
-:2: undefined local variable or method `foo' for #<Object:0x40283118> (NameError)
---
  NameError

Though, the above will successfully done by irb. 

>> eval "foo = 0"
=> 0
>> foo
=> 0

Ruby evaluates a code after reading entire of code and determination
of the scope of local variables. On the other hand, irb do
immediately. More precisely, irb evaluate at first

  evel "foo =0" 

then foo is defined on this timing. It is because of this
incompatibility.

If you'd like to detect those differences, begin...end can be used:

>> begin
?>   eval "foo = 0"
>>   foo
>> end
NameError: undefined local variable or method `foo' for #<Object:0x4013d0f0>
(irb):3
(irb_local_binding):1:in `eval'


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