Subsets with Reference Semantics
Returns or changes parcel contents
Checks whether an object is a parcel
Subsets with Reference Semantics
Create a reference to a subset of an object
Unwrap contents of a parcel into a new variable
Wrap an expression and its environment into a parcel.
Convenience function to create a parcel containing a refset.
Provides subsets with reference semantics, i.e. subsets which automatically reflect changes in the original object, and which optionally update the original object when they are changed.