FA-17203 / Floating-point arithmetic / Member archive

Cube root returns the magnitude for negative inputs · case 03

Cube root returns the magnitude for negative inputs.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Real cube root on finite binary64 inputs. Split magnitude with frexp, divide exponent by three with floor division, and apply residual exponent before rooting. Return signed zero unchanged. Finite results are rendered to eleven significant decimal digits; modeled domain violations and arithmetic errors are explicit strings.

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 cube	`"3"`	`"-3"`	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.