FA-16215 / Floating-point arithmetic / Member archive

Inverse tangent drops odd symmetry · case 05

Inverse tangent drops odd symmetry.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Evaluate inverse hyperbolic tangent on [-1,1], with signed infinite endpoints and a domain marker outside. 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
tiny negative	`"4.3368086899e-18"`	`"-4.3368086899e-18"`	Failed

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