ValuePreprocessingFunction

is an option for functions such as PersistentSymbol and InitializationValue that specifies a function to apply to a new value that is being assigned.

Details

When a value is to be assigned with PersistentSymbol["name",…]=value or InitializationValue["name",…]=value, the setting of the ValuePreprocessingFunction option is applied to value; the result is then assigned. If the result is $Failed, no assignment is done.
The default setting is ValuePreprocessingFunction->Identity, which does not modify the value to be assigned.
Settings for ValuePreprocessingFunction are typically done for the "Installation" persistence location.

Examples

Define a value preprocessing function that accepts only integers:

Set up a default value and the value preprocessing function for a persistent value named "int":

Assign an integer at any persistence location:

Assigning anything else generates an error, and the assignment is not performed:

Top