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Pivot substitutes a null element for an absent cell · case 02

Pivot substitutes a null element for an absent cell.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

Pivot [row-id,category,value] into [row-id,list-for-category...] using the caller category order. Each cell is an ordered bag list. Unknown categories do not populate cells but retain their row identity; absent cells are empty lists and null values remain elements.

Why this case matters

A bounded deterministic data engine model makes representation and changelog faults reproducible.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
unknown-only row	`[[1, [null]]]`	`[[1, []]]`	Failed

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