FA-15898 / Floating-point arithmetic / Member archive

An equal-value early return preserves the wrong zero sign · case 03

An equal-value early return preserves the wrong zero sign.

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
negative zero equality	`0`	`9223372036854775808`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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