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Fractional position allocation: an open upper bound uses the largest digit instead of the base · case 03

Appending after a position ending in 8 or 9 goes deeper instead of using the free top digit.

Member previewVariant 3 · 3 implementations · 10 checks per implementation

Case contract

Starting from the given sorted positions, positions are digit lists in base 10 compared lexicographically and never ending in 0. Inserting at list index i allocates between the neighbours p (or [] at the start) and q (or [] at the end): walking depth d, lower digit a is p[d] or 0, upper digit b is q[d] while q still constrains (else 10); if b - a > 1 append (a+b)//2 and stop, else append a, and q stops constraining once a < b. Return positions as dotted strings in list order.

Why this case matters

Sequence CRDTs such as Logoot and LSEQ assign dense identifiers so that concurrent inserts never need renumbering.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
first insert	`["4"]`	`["5"]`	Failed

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