Talk:Tree datastructures
Attribution
My thanks to Ralf Ebert who asked this question on Stack Overflow which introduced me to the indent form. I answered his question then thought of RC. --Paddy3118 (talk) 08:28, 17 October 2019 (UTC)
Good idea for a task – a couple of thoughts.
This seems a promising kind of task – perhaps worth linking to the Functional Coverage Tree task, so that the latter can use outline parsing routines shaped up here.
A couple of thoughts:
- Perhaps JSON serialisations, both for the nested and numbered data types ?
- Unicode characters beyond the narrowly Anglo-Saxon alphabet ? Hout (talk) 23:09, 15 October 2019 (UTC)
The simplest nested JSON output (each node a value+list pair) would be:
[["RosettaCode",[
["rocks",[
["code",[]],
["comparison",[]],
["wiki",[]]
]],
["mocks",[
["golfing",[]]
]]
]]] Hout (talk) 23:43, 15 October 2019 (UTC)
Incidentally, do you feel strongly committed to that particular outline ? For some reason the word 'mock' jars a little (perhaps particularly now that we are beginning to understand more about the destructive potential of digital networks). Hout (talk) 23:43, 15 October 2019 (UTC)
Similarly, the simplest JSON output list for integer+value tuples would be:
[[0,"RosettaCode"], [1,"rocks"], [2,"code"], [2,"comparison"], [2,"wiki"], [1,"mocks"], [2,"golfing"]]
Hout (talk) 23:46, 15 October 2019 (UTC)
- Good Q's. I have a cold (streaming eyes), and will get back to you tomorrow? Thanks. --Paddy3118 (talk) 13:33, 16 October 2019 (UTC)
- On those questions.
- JSON: I didn't want to restrict the task that way, as some could make an equal claim for XML or lisp lists - I thought I'd stay more neutral on that point.
- The outline: There should be one, and only one, blah-de-blah :-) Well actually I loved my rocks/mocks pun too much and just slapped in "golfing" as a bad afterthought. I think it is very useful to have the one tree for all language examples, but I stopped mocking golfing years and years ago - its not for RC, but not for mocking IMHO. I have tried for a late save with a note, but is it too late to ask for all examples to update to use just "trolling"?
- Your task statement sensibly specifies code that is outline-independent, so any change would, if the code is working, be a quick copy-paste.
- (I can speak for 4 of the 7 current entries, all of which I would very happy to change :-)
- To be honest, I feel a little embarrassed by any 'mocking' / 'trolling' references – people are dying from it at the moment – I think I would feel less uneasy with something a bit more plausible and motivating – maybe something that gave a sense of the contexts in which one might actually want to work with a tree structure, or something related to the content ? Hout (talk) 08:41, 17 October 2019 (UTC)
And when comparison has children?
--Nigel Galloway (talk) 13:03, 16 October 2019 (UTC)
Depends, of course, on the implementation of equality in each language. For JS I have had to hand-write a recursive eq. Haskell's Data.Tree module includes a Tree instance for the Eq class. Python's (==) equality is recursive out of the box. Hout (talk) 13:27, 16 October 2019 (UTC)
- Hi, I added a note to the task to try and downplay the significance of this part of the task after this query as I would like the datastructures and the conversion between them to be central. --Paddy3118 (talk) 08:40, 18 October 2019 (UTC)
Deriving a tree from a list of lines with their indent levels
For what its worth, a declarative description which is also a recursive algorithm might look something like:
If a forest is understood as a list of trees,
then the forest structure of an indented outline is either
an empty list,
(if the outline contains no lines)
or a list with a tree at its head, and a tail which is a forest.
The head tree:
- has the first line of the outline as its value
- and has a (possibly empty) child list
which is the forest structure of all the lines (if any) which:
- follow the first line,
- and precede its next peer
(the next line that shares the first's indent level)
The tail forest has the structure of the remaining outline,
- from the next line which shares the indent level of the first line,
- to the last line of the outline.
Generic tree to indent-type datastructure conversion
The following is the diagram from the Tree traversal task annotated with depth information for the nodes:
:NODE_DEPTH
1 :0
/ \
/ \
/ \
2 3 :1
/ \ /
4 5 6 :2
/ / \
7 8 9 :3
A preorder traversal of the tree outputting (node_depth, node_name) pairs will generate the indent form of this and other rooted trees. --Paddy3118 (talk) 21:43, 19 October 2019 (UTC)
Task tree in dot format, and diagram
<lang dot>digraph rc {
node [fontsize=12 height=0.1 nodesep=0.25 width=0.1] RosettaCode -> rocks rocks -> code rocks -> comparison rocks -> wiki RosettaCode -> mocks mocks -> trolling RosettaCode [color=brown fontcolor=green fontname=bold]
}</lang>
