a) The ability to define within arc what happens when a list is
used as function, instead of it being predefined in scheme
b) The ability to do this for any type and custom types.
And potentially:
c) For annotated values to be able to do this per-object,
by storing an extra field in there that is the getter,
where the default value is the one for the type.
E.g: (annotate 'blabla value getter)
If there is no getter, then use the one for type 'blabla
