From: Hans Fugal <fugalh@...>
Date: 2007-02-19T14:55:17+09:00
Subject: yaml and self-referential data

I have a data structure (Arrays and Hashes mixed in a soup) that is 
fairly self-referential, i.e. it has cycles. When I try to do 
foo.to_yaml, it complains:

/opt/local/lib/ruby/1.8/yaml.rb:382:in `quick_emit': stack level too 
deep (SystemStackError)
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:164:in `to_yaml'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `node_export'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `add'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `to_yaml'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:40:in `each'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:40:in `to_yaml'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:39:in `map'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:39:in `to_yaml'
          ... 6502 levels...
         from /opt/local/lib/ruby/1.8/yaml.rb:387:in `emit'
         from /opt/local/lib/ruby/1.8/yaml.rb:387:in `quick_emit'
         from /opt/local/lib/ruby/1.8/yaml/rubytypes.rb:107:in `to_yaml'
         from ./yaml.rb:43

However, on the small testing scale it works fine:

---
- &id004
   name: foo
   famc: &id002
     parents:
     - &id001
       name: bar
       fams: *id002
       famc: &id005
         children:
         - *id001
     - &id003
       name: baz
       fams: *id002
       famc: &id006
         children:
         - *id003
     children:
     - *id004
- *id001
- *id003
- *id002
- *id005
- *id006

Is there anything I can do to help the to_yaml method along? Maybe tell 
it to be eager about using aliases or something?