Fix behavior of prefix increment/decrement

[mborland]

Closes: #277

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.63%. Comparing base (babec31) to head (944ac56).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #278      +/-   ##
===========================================
- Coverage    99.64%   99.63%   -0.02%     
===========================================
  Files           50       50              
  Lines         5073     4886     -187     
  Branches      1421     1421              
===========================================
- Hits          5055     4868     -187     
  Misses          18       18              

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