3.3.8 Persist

This action applies when the active expression is a substitution rule, a transform rule or a property list. A substitution rule is just an equation originating in an identity (see §3.3.4), whereas a transform has its own special syntactic form: ʈ pattern → replacement, constraint (see §3.3.5). A property list is a set of substitution and transform rules (see §3.3.6).

To create a new substitution rule, you must start with an identity equation. Alternatively, you can recall an equation from the substitutions display. You can then manipulate either side to create an equation in which the left and right sides are different, but as long as the undo history leads back to either an identity equation or a recalled equation, the relationship is valid.

Having created a suitable rule or property list, select it and touch Persist . The expression is added to the appropriate collection, depending on whether it is an substitution rule, a transform rule or a property list. Rules and property lists can be viewed by selecting Substitutions , Transforms or Properties under the Display menu item.

To remove a substitution or transform rule, see §8.1.7. To remove a property list, see §8.1.8.