FA-15850 / Floating-point arithmetic / Member archive

Sign bit contaminates the exponent field · case 05

Sign bit contaminates the exponent field.

Member previewVariant 5 · 3 implementations · 10 checks per implementation

Case contract

Decode an unsigned 64-bit IEEE binary64 encoding into sign, kind, unbiased exponent, integer significand, quiet flag and payload. Nonfinite fields use null; zero and subnormal exponents are -1022.

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	`[-1, "normal", 1025, 4503599627370496, null, null]`	`[-1, "zero", -1022, 0, null, null]`	Failed

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

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