FA-15958 / Floating-point arithmetic / Member archive

Nearest rounding loses the round bit after a guard · case 03

Nearest rounding loses the round bit after a guard.

Member previewVariant 3 · 3 implementations · 12 checks per implementation

Case contract

Round a nonnegative integer significand q with guard, round and sticky bits. Modes are nearest-even, nearest-away, zero, up, down; sign is +1 or -1. Return rounded signed integer, inexact flag, and whether rounding incremented the magnitude.

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
above tie round	`[6, true, false]`	`[7, true, true]`	Failed

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