FA-15908 / Floating-point arithmetic / Member archive

Positive adjacency always increments the encoding · case 03

Positive adjacency always increments the encoding.

Member previewVariant 3 · 3 implementations · 12 checks per implementation

Case contract

Return the binary64 bit pattern one representable step from x toward y, or canonical quiet NaN for NaN operands. Equal operands return the exact bits of y, including zero sign.

Why this case matters

An offline floating representation model isolates a reproducible arithmetic fault.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
positive reverse	`4607182418800017409`	`4607182418800017407`	Failed

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