Talk:Tree datastructures: Difference between revisions
→One description (and algorithm) for the indents -> tree relationship
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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. [[User:Hout|Hout]] ([[User talk:Hout|talk]]) 13:27, 16 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:
<pre>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 child list
which is the forest structure of all the lines:
- following the first line,
- and preceding the 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.</pre>
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