FA-17110 / Floating-point arithmetic / Member archive

Midpoint computes an exact negative-zero endpoint through addition · case 05

Midpoint computes an exact negative-zero endpoint through addition.

Member previewVariant 5 · 3 implementations · 9 checks per implementation

Case contract

Finite ordered binary64 midpoint rendered as hex. Opposite-sign endpoints use half-sums to avoid difference overflow; same-sign endpoints use a difference to preserve subnormal increments. Exact equal endpoints preserve their bits.

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 equal	`"0x0.0p+0"`	`"-0x0.0p+0"`	Failed

MEMBER ARCHIVE

The complete case is available to members.

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

Member access is invitation-based. Sign in with your invited account to inspect the sources.