ara.t.howard / noaa.gov wrote:

> but is a nil value by default ok?

  >> require 'yaml'
  >> hsh = {'to' => 'ara.t.howard / noaa.gov', 'x-mail-count' => 178223, 
'from' => 'why / ruby-lang.org'}
  >> hsh.to_yaml_style
  => nil

If you really need to sniff, I'd use YAML::Syck::VERSION.  In case you 
encounter someone who'se upgraded their extension.

  why@stungun ~ $ ~/sand/RUBY-1_8_4/bin/ruby -v -ryaml -e 'p 
YAML::Syck::VERSION'
  ruby 1.8.4 (2005-12-24) [i686-linux]
  "0.60"

  why@stungun ~ $ ~/sand/RUBY-1_8_3/bin/ruby -v -ryaml -e 'p 
YAML::Syck::VERSION'
  ruby 1.8.3 (2005-09-21) [i686-linux]
  "0.60"

  why@stungun ~ $ ~/sand/RUBY-1_8_2/bin/ruby -v -ryaml -e 'p 
YAML::Syck::VERSION'
  ruby 1.8.2 (2004-12-25) [i686-linux]
  "0.45"

There shouldn't be any 0.5x Sycks floating around in stable Ruby releases.

_why