Feature: Ancestor search

[holke]

Closes #1715

Describe your changes here:

Currently waiting for #1640 to merge.
Will add a description afterwards.

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 46 lines in your changes missing coverage. Please review.

Project coverage is 73.88%. Comparing base (9e6f427) to head (8f9b60e).
Report is 26 commits behind head on main.

Files with missing lines	Patch %	Lines
src/t8_forest/t8_forest_private.cxx	0.00%	46 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1714      +/-   ##
==========================================
- Coverage   74.06%   73.88%   -0.18%     
==========================================
  Files          99       99              
  Lines       18616    18667      +51     
==========================================
+ Hits        13788    13793       +5     
- Misses       4828     4874      +46     

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[Davknapp]

A first round of remarks! Thanks for this addition!

[Davknapp]

Have you opened issues for these Todos? That way they do not get lost that easily.

[Davknapp]

I think we should be consistent here with the std and return the index of the last element if no such element exist.

[Davknapp]

additional remark, but maybe not necessary to react. I would find it more logical to also use std::upper_bound in that case. I know with the right lambda they are equivalent, but it feels right.

[Davknapp]

Suggested change

	t8_forest_element_is_ancestor (const t8_scheme *scheme, t8_eclass_t eclass, const t8_element_t *element_A,
	t8_forest_element_is_ancestor (const t8_scheme *scheme, const t8_eclass_t eclass, const t8_element_t *element_A,

[Davknapp]

Suggested change

	/** Query whether one element is an ancestor of the other.
	/** Query whether element A is an ancestor of the element B.

Otherwise it sounds like both possibilities are checked, but this is not the case, as far as I understand the code.