Relative Activation Numbers

A relative activation number is either zero or a negative integer. A relative activation number specifies the number of activations to count backwards from the most recent activation. The number 0 denotes the most recent activation. The activation directly preceding the most recent activation is denoted by -1. For example, if there have been five activations of the procedure FACTORIAL, FACTORIAL:0 refers to the fifth activation and FACTORIAL:-2 refers to the third activation. This activation can also be referred to as FACTORIAL:3 (that is, using the absolute activation number 3).