FA-17114 / Floating-point arithmetic / Member archive

Midpoint silently sorts reversed endpoints · case 04

Midpoint silently sorts reversed endpoints.

Member previewVariant 4 · 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
reverse	`"0x1.2000000000000p+2"`	`"invalid"`	Failed

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