FA-12127 / Robotics frame conventions / Member archive

A scalar-last quaternion is read by a scalar-first adapter · case 02

A scalar-last quaternion is read by a scalar-first adapter.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

Convert a four-element xyzw quaternion representation to wxyz without changing signs, magnitude, or axis order. This adapter does not normalize or choose equivalent quaternion signs.

Why this case matters

Robot adapters must preserve the declared frame, reference point, and representation conventions across interfaces.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
identity	`[0, 0, 0, 1]`	`[1, 0, 0, 0]`	Failed

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