Consting eclass arguments in many functions.

[jmark]

Describe your changes here:

Adding const modifier to all eclass_scheme pointers in the function signatures of element_interface routines. This involved a lot of small changes in many files. Basically adding const modifiers at the right places.

All these boxes must be checked by the reviewers before merging the pull request:

As a reviewer please read through all the code lines and make sure that the code is fully understood, bug free, well-documented and well-structured.

• The author added a BSD statement to doc/ (or already has one)

• The code compiles without warning in debugging and release mode, with and without MPI (this should be executed automatically in a github action)

  If the Pull request introduces code that is not covered by the github action (for example coupling with a new library):

  • Should this use case be added to the github action?
  • If not, does the specific use case compile and all tests pass (check manually)

• All tests pass (in various configurations, this should be executed automatically in a github action)

• New source/header files are properly added to the Makefiles

• New Datatypes are added to t8indent_custom_datatypes.txt

• The reviewer executed the new code features at least once and checked the results manually

• The code is covered in an existing or new test case

• New tests use the Google Test framework

• The code follows the t8code coding guidelines

• The code is well documented

• All function declarations, structs/classes and their members have a proper doxygen documentation

• All new algorithms and data structures are sufficiently optimal in terms of memory and runtime (If this should be merged, but there is still potential for optimization, create a new issue)

• Testing of this template: If you feel something is missing from this list, contact the developers

[ililikakis]

Please update the branch to fix the open merge conflicts. Besides that, everything looks good so far.

I saw that other arguments in addition to t8_eclass_scheme_c can also be set const on some element_interface routines. For example t8_element_get_face_corner (const t8_eclass_scheme_c *ts, const t8_element_t *elem, int face, int corner). Do you like to do this in the same run, or should I open a new PR for it?

[jmark]

Please update the branch to fix the open merge conflicts. Besides that, everything looks good so far.

Done.

I saw that other arguments in addition to t8_eclass_scheme_c can also be set const on some element_interface routines. For example t8_element_get_face_corner (const t8_eclass_scheme_c *ts, const t8_element_t *elem, int face, int corner). Do you like to do this in the same run, or should I open a new PR for it?

Good point! But the title of ths PR explicity says "Consting eclass arguments ...". I would open another PR for this.