Use x.data instead of x.begin when doing pointer arithmetic

[LegalizeAdulthood]

Fixes#93

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.35%. Comparing base (2875284) to head (d577f19).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@ Coverage Diff @@## develop #101 +/- ##
========================================
Coverage 99.35% 99.35% ========================================
Files 168 168 Lines 6833 6833 ========================================
Hits 6789 6789 Misses 44 44 

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