FA-5409 / Integer arithmetic / Member archive

Isolate lowest set bit · case 04

Clearing the low bit is confused with extracting it.

Member previewVariant 4 · 3 implementations · 4 checks per implementation

Case contract

Integer arguments; denominators, steps, moduli, and bit widths are positive. Unsigned word inputs fit the specified width except where masking is explicitly the operation. Sequence sizes are nonnegative. n is nonnegative; retain exactly its least significant one, or return zero for zero. Exact operational definition: n & -n

Why this case matters

Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Integer mathematics results depend on the stated convention.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
fixture 1: (12,)	`8`	`4`	Failed

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