From: Dossy <dossy@...>
Date: 2003-01-04T05:58:49+09:00
Subject: Re: dump depth argument

On 2003.01.04, Tom Sawyer <transami@transami.net> wrote:
> On Friday 03 January 2003 12:05 pm, Dossy wrote:
> > $ ri Marshal#dump
[...]
> 
>  Dossy,
> 
> you crack me up. i've read this! that's what i don't understand. according to 
> it, anIO is optional but when i try the second example it bombs. not very 
> optional. maybe i just don't know how to read this correctly but it seems to 
> be acting more like:
> 
> 	dump( anObject [, anIO [, limit=1 ] ] )
> 
> what am i missing?

irb(main):007:0> class Foo
irb(main):008:1>   def initialize(x)
irb(main):009:2>     @foo = x
irb(main):010:2>   end
irb(main):011:1> end
nil

irb(main):012:0> class Bar
irb(main):013:1>   def initialize(x)
irb(main):014:2>     @bar = x  
irb(main):015:2>   end
irb(main):016:1> end
nil

irb(main):017:0> foo = Foo.new(Bar.new("baz"))
#<Foo:0x40274e2c @foo=#<Bar:0x40274e40 @bar="baz">>

irb(main):018:0> Marshal.dump(foo)
"\004\006o:\010Foo\006:\t@fooo:\010Bar\006:\t@bar\"\010baz"

irb(main):032:0> Marshal.dump(foo, 2)
ArgumentError: exceed depth limit
        from (irb):32:in `dump'
        from (irb):32

While the limit would be more useful if it weren't a hard limit but
instead a suggested limit, it does behave as documented, IMHO.

rb(main):090:0> rdio, wrio = IO.pipe
[#<IO:0x40272c30>, #<IO:0x40272c1c>]

irb(main):091:0> Marshal.dump(foo, wrio, 3); wrio.print "\n"; wrio.flush
#<IO:0x40272c1c>

irb(main):092:0> rdio.readline
"\004\006o:\010Foo\006:\t@fooo:\010Bar\006:\t@bar\"\010baz\n"

As I said, it'd be more interesting if the limit parameter to
Marshal#dump simply stopped the recursive traversal of child
objects at limit, instead of throwing an error ... but, I'm
not the language implementer, so it's not my call to make ...

-- Dossy

-- 
Dossy Shiobara                       mail: dossy@panoptic.com 
Panoptic Computer Network             web: http://www.panoptic.com/ 
  "He realized the fastest way to change is to laugh at your own
    folly -- then you can let go and quickly move on." (p. 70)