A convenient translation-function parameterization

A novel parameterization is given for one type of single-symmetry-element translation function, the Q functions of Tollin [Acta Cryst. (1966), 21, 613-614]. This parameterization enables the straightforward computation of these for any symmetry element. A computationally convenient form of the Q-function expression is given. Examples of Q for a selection of symmetry elements, illustrating some of the simplifications of the general form.