some cleanup in the Lanczos files

[manuschneider]

Avoids function names starting with _ followed by upper case

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.34%. Comparing base (e87c3a2) to head (432eaaa).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/linalg/Lanczos_Exp.cpp	71.42%	22 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #726      +/-   ##
==========================================
+ Coverage   32.35%   35.34%   +2.99%     
==========================================
  Files         215      215              
  Lines       36363    33014    -3349     
  Branches    14597    13136    -1461     
==========================================
- Hits        11764    11670      -94     
+ Misses      22659    19430    -3229     
+ Partials     1940     1914      -26     

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[IvanaGyro]

Using unnamed namespace for internal linkage is a preferred style in modern C++.

Example: https://google.github.io/styleguide/cppguide.html#Internal_Linkage

[manuschneider]

The internal functions should have access to the namespace cytnx, though. It seems there is no good solution with namespaces for this - if I put an unnamed namespace within the cytnx namespace, then the code is not hidden but visible everywhere in cytnx. Static functions seem the better solution here.

[ianmccul]

It would only be visible if the unnamed namespace was in a header that was included elsewhere.

[IvanaGyro]

Remove unused code?

[IvanaGyro]

BTW, if you are modifying all function names in the file, you can just use PascalCase which is requested in the coding style.

[manuschneider]

BTW, if you are modifying all function names in the file, you can just use PascalCase which is requested in the coding style.

I see that the google style sheet suggests this. However, the current API uses snake_style for all functions, and it would not make sense to change the whole API for this. To me, it makes more sense to stick to this style which is already fixed by the API, instead of mixing with google's style convention.