Support vec with RectPolynomial and fix sum ordering

[dlfivefifty]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.44%. Comparing base (6fb10b9) to head (efd3c18).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #208      +/-   ##
==========================================
+ Coverage   96.42%   96.44%   +0.02%     
==========================================
  Files           7        7              
  Lines        1034     1040       +6     
==========================================
+ Hits          997     1003       +6     
  Misses         37       37              

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