ar(q)</tt></p>
<h2>Description</h2>
<p>
These two functions extract the scalar component of a quaternion.
The result is a real (or a complex value if the quaternion has
complex components).
</p>
<p>
The two functions differ in their behaviour when given a pure quaternion
(that is a quaternion with no scalar part). The function <tt>s</tt>
raises an error in this circumstance, whereas <tt>scalar</tt> returns
a zero array of the same size as the pure quaternion, with the same class
as the components of the qua