# Deep YAML **URL:** \ **Category:** Ruby\ **Created:** [August 2, 2007, 5:50am UTC](https://www.ruby-forum.com/t/deep-yaml/111049 "2007-08-02T05:50:59Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Hans\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a587f6/32.png) [@Hans\_F](https://www.ruby-forum.com/u/Hans_F)\ **Post date:** [August 2, 2007, 5:50am UTC](https://www.ruby-forum.com/t/deep-yaml/111049/1 "2007-08-02T05:50:59Z")
I’m toying with GEDCOM again, and trying to write out the YAML equivalent of a GEDCOM file (just for kicks, mainly). It might look like this (edited for brevity): 0 @I1@ INDI 1 NAME Victoria /Hanover/ 1 TITL Queen of England 1 FAMS @F1@ 1 FAMC @F2@ 0 @I2@ INDI 1 NAME Albert Augustus Charles// 1 TITL Prince 1 FAMS @F1@ 1 FAMC @F3@ … 0 @F1@ FAM 1 HUSB @I2@ 1 WIFE @I1@ 1 CHIL @I3@ The stuff between @ symbols can be thought of as pointers (defined when in front, referenced when in back). The natural way to store this in ruby is to set up a hash for these pointer names while parsing and store the actual object references. i.e. victoria[‘FAMS’] does not equal “@F1@” but the actual family Hash. Now, when trying to dump the ultimate data structures (which is made up entirely of Arrays, Hashes, and Strings), you can see that by the very nature of the data almost everything in the file will be referenced in one long link from the root person, who is usually at the beginning. So basically the first entry in the YAML top-level array would nestingly include every other individual and family. This naturally makes for a very deep structure, which is neither human-friendly nor stack-friendly. In fact even modest GEDCOM files break the stack during to\_yaml with this approach. Is there no way to have yaml break deep nesting with an ID reference? Or better yet, use an ID at any point other than the shallowest point where that object occurs? ---
**Author:** ![Hans\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a587f6/32.png) [@Hans\_F](https://www.ruby-forum.com/u/Hans_F)\ **Post date:** [August 2, 2007, 12:43pm UTC](https://www.ruby-forum.com/t/deep-yaml/111049/2 "2007-08-02T12:43:52Z")
Hans F. wrote: > I’m toying with GEDCOM again, and trying to write out the YAML > equivalent of a GEDCOM file (just for kicks, mainly). > > It might look like this (edited for brevity): > > 0 @I1@ INDI > 1 WIFE @I1@ > 1 CHIL @I3@ > > Is there no way to have yaml break deep nesting with an ID reference? Or > better yet, use an ID at any point other than the shallowest point where > that object occurs? YAML will make an ID reference rather than inserting the object if it has already encountered that object as it traverses the object tree. You just have to make sure that it encounters the objects in the correct order. Here’s my reasoning. We are trying to dump a really deep tree to YAML: # first build the tree: deeptree = [] curr = deeptree refs = [] 5000.times do |i| n = [i, []] curr \<\< n curr = n[1] refs \<\< n end # then try and dump it: deeptree.to\_yaml #=\> fails with stack error refs.to\_yaml #=\> fails with stack error refs.reverse.to\_yaml #=\> succeeds! Deeptree looks like: [1, [2, [3, [4, []]]]] which fails because its so deep. Refs looks like: [ [1, [2, [3, [4, []]]]], [2, [3, [4, []]]], [3, [4, []]], [4, []], [] ] which fails because the first element is so deep. refs.reverse looks like: [ [], [4, []], [3, [4, []]], [2, [3, [4, []]]], [1, [2, [3, [4, []]]]] ] which works because at each step YAML can insert an object reference because it has already encountered the second array element in the previous step. So in your case, instead of just saving the family tree, save an array containing references to all members of the tree. Make sure to start with the leaves of the tree and work your way up through the ancestors. When you reload the last element of the array is your complete tree. hope this helps, Dan * * * Illustrations: irb\> arr =\> [0, [1, [2, [3, [4, []]]]]] irb\> refs =\> [[1, [2, [3, [4, []]]]], [2, [3, [4, []]]], [3, [4, []]], [4, []], []] ## irb\> puts arr.to\_yaml - 0 - - 1 - - 2 - - 3 - - 4 - [] =\> nil ## irb\> puts refs.to\_yaml - - 1 - &id001 - 2 - &id002 - 3 - &id003 - 4 - &id004 [] - \*id001 - \*id002 - \*id003 - \*id004 =\> nil ## irb\> puts refs.reverse.to\_yaml - &id001 [] - &id002 - &id003 - &id004 - - 1 - \*id004 =\> nil ---
**Author:** ![Hans\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a587f6/32.png) [@Hans\_F](https://www.ruby-forum.com/u/Hans_F)\ **Post date:** [August 2, 2007, 3:36pm UTC](https://www.ruby-forum.com/t/deep-yaml/111049/3 "2007-08-02T15:36:08Z")
Daniel L. wrote: > # then try and dump it: > > deeptree.to\_yaml #=\> fails with stack error > refs.to\_yaml #=\> fails with stack error > refs.reverse.to\_yaml #=\> succeeds! I thought of this, ufortunately this data is more like a doubly-linked tree. i.e. if you reverse it you still get the same behavior, just from a different angle. ---
**Author:** ![Hans\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a587f6/32.png) [@Hans\_F](https://www.ruby-forum.com/u/Hans_F)\ **Post date:** [August 2, 2007, 3:50pm UTC](https://www.ruby-forum.com/t/deep-yaml/111049/4 "2007-08-02T15:50:28Z")
Hans F. wrote: > Daniel L. wrote: > > > # then try and dump it: > > > > deeptree.to\_yaml #=\> fails with stack error > > refs.to\_yaml #=\> fails with stack error > > refs.reverse.to\_yaml #=\> succeeds! > > I thought of this, ufortunately this data is more like a doubly-linked > tree. i.e. if you reverse it you still get the same behavior, just from > a different angle. Because there are links going up the tree as well as down? Dan ---
**Author:** ![Hans\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a587f6/32.png) [@Hans\_F](https://www.ruby-forum.com/u/Hans_F)\ **Post date:** [August 2, 2007, 12:49pm UTC](https://www.ruby-forum.com/t/deep-yaml/111049/5 "2007-08-02T12:49:37Z")
Daniel L. wrote: > # first build the tree: > > deeptree = [] > curr = deeptree > refs = [] > 5000.times do |i| > n = [i, []] > curr \<\< n > curr = n[1] > refs \<\< n > end Oops, that actually makes a tree that looks like this: [[0, [[1, [[2, [[3, [[4, []]]]]]]]]]] I meant this: refs = [] deeptree = [] curr = deeptree 5000.times do |i| n = [] curr \<\< i curr \<\< n curr = n refs \<\< n end which does look like this: [0, [1, [2, [3, [4, []]]]]] soz, Dan ---
**Author:** ![Hans\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/a587f6/32.png) [@Hans\_F](https://www.ruby-forum.com/u/Hans_F)\ **Post date:** [August 2, 2007, 5:16pm UTC](https://www.ruby-forum.com/t/deep-yaml/111049/6 "2007-08-02T17:16:27Z")
Daniel L. wrote: > Because there are links going up the tree as well as down? > > Dan Yes, exactly. Links from parent to child, and also from child to parent (and from person to family and family to person).