A.5 Mapping pseudo-objects to Lisp

A.5.1 Narrowing

In line with the other language binding, we define an operation for narrowing an object reference. The code:

(op:narrow class-symbol object-refence)

attempts to narrow the given object reference into an object of the named client-side class.

For example, to narrow an client-side value stored inaccount-ref, into an object of typeBankingdemo:Checkingaccount:

(when (op:Is_a account-ref 
        (op:id Bankingdemo:_Tc_Checkingaccount))
   (setf account-ref 
   (op:narrow 'Bankingdemo:Checkingaccount account-ref)))