Add abs_diff function

[mborland]

Closes: #84

[cppalliance-bot]

An automated preview of the documentation is available at https://105.safe-numbers.prtest3.cppalliance.org/libs/safe_numbers/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-02-23 20:04:13 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.5%. Comparing base (544c1a0) to head (6926cc2).
⚠️ Report is 10 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #105     +/-   ##
=========================================
+ Coverage     98.5%   98.5%   +0.1%     
=========================================
  Files          113     114      +1     
  Lines         7554    7654    +100     
  Branches      2697    2746     +49     
=========================================
+ Hits          7439    7539    +100     
  Misses          42      42             
  Partials        73      73             

Files with missing lines	Coverage Δ
include/boost/safe_numbers/detail/type_traits.hpp	100.0% <ø> (ø)
include/boost/safe_numbers/integer_utilities.hpp	100.0% <100.0%> (ø)
test/test_abs_diff.cpp	100.0% <100.0%> (ø)

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