YAML issue with Set?

ruby-talk
1

What am I doing wrong?

#!/opt/local/bin/ruby

···

###############################
require 'set'
require 'yaml'
require 'tempfile'

def tempname(basename)
  file = Tempfile.new(basename)
  file.close(false)
  file.path
end

class U
  attr_accessor :name
  def initialize(n)
  @name = n
  end
  def ==(other)
    name == other.name
  end
end

set = Set.new
set.add(U.new("one"))
set.add(U.new("two"))

filename = tempname("set_yaml")
File.open(filename, "w") {|f| YAML.dump(set, f)}

another_set = YAML.load(File.open(filename))

puts "#{set == another_set}"
###############################

The result that I get is the following:

###############################
xxx:~ piergiulianobossi$ ./set_yaml.rb
/opt/local/lib/ruby/1.8/yaml.rb:133:in `load': syntax error on line 3,
col -1: ` name: one (ArgumentError)
  : true

  !ruby/object:U ?
    name: two
  : true

' from /opt/local/lib/ruby/1.8/yaml.rb:133:in `load'
        from ./set_yaml.rb:30
###############################

Running ruby on Mac OS/X 10.4

###############################
xxx:~ piergiulianobossi$ ruby -v
ruby 1.8.5 (2006-08-25) [i686-darwin8.8.1]
###############################

2

Alle sabato 3 marzo 2007, thebox ha scritto:

What am I doing wrong?

As far as I can tell (I'm not a YAML expert), no. I've made a few trials, and
it seems that class Hash (which is used internally by Set), has problems with
loading / dumping when keys are custom classes. For instance, using irb
(ruby -v gives ruby 1.8.5 (2006-12-25 patchlevel 12) [i686-linux], on gentoo)
:

require 'yaml'

=> true

class C
end

=> nil

c=C.new

=> #<C:0xb78bd5b4>

h={c=>'test'}

=> {#<C:0xb78bd5b4>=>"test"}

str=YAML.dump h

=> "--- \n!ruby/object:C ? {}\n: test\n\n"

h1=YAML.load str

ArgumentError: syntax error on line 2, col -1: `: test

'
        from /usr/lib/ruby/1.8/yaml.rb:133:in `load'
        from /usr/lib/ruby/1.8/yaml.rb:133:in `load'
        from (irb):7

YAML can't convert the string it just produced to a Hash. I've been able (with
blind trials and using the documentation at
http://yaml4r.sourceforge.net/cookbook/, in particular the section on ranges)
to modify the string produced by dump to make it load again. The original
string is:

···

---
!ruby/object:C ? {}
: test

The modified one is:

---
? !ruby/object:C {}
: test

It seems that the problem arises from the fact that the dump puts the ?
(which, if I understand correctly, should mark a hash key) after the type of
the object (the !ruby/object:C part), while load (correctly, I think) wants
it before the type.

There is a bug report for this problem:
http://rubyforge.org/tracker/?group_id=426&atid=1698&func=detail&aid=8886

Stefano

3

As far as I can tell (I'm not a YAML expert), no. I've made a few trials, and
it seems that class Hash (which is used internally by Set), has problems with
loading / dumping when keys are custom classes. For instance, using irb
(ruby -v gives ruby 1.8.5 (2006-12-25 patchlevel 12) [i686-linux], on gentoo)
:

[...]

There is a bug report for this problem:http://rubyforge.org/tracker/?group_id=426&atid=1698&func=detail&aid=\.\.\.

Thanks, this makes a lot of sense. I'll stay away from Hash-based
collection with custom classes and YAML for now.

Giuliano

···

On Mar 3, 11:07 am, Stefano Crocco <stefano.cro...@alice.it> wrote: