SICM 2nd ed. 1.2

SICM

    /// https://en.wikipedia.org/wiki/Euler_angles
    struct EulerAngle3<R> { α: R, β: R, γ: R }
    struct Point<R> { x: R, y: R, z: R }
    struct Pin<R> {
        /// The location of the pin's center of gravity.
        center: Point<R>,

        /// The angle with the positive Z axis of some distinguished point
        /// on the pin that is off the pin's axis of symmetry.
        orientation: EulerAngle3<R>
    }
    type System<R> = [Pin<R>; 6];