[clean-list] Updating unique structures in unique structures in unique structures

[Norbert Zeh]

When I first got to know Clean, I came from the Haskell side and was 
impressed that Clean had found a way to make array updates efficient while 
maintaining referential transparency.  Now I've run into my first round of 
problems with unique objects, and I'd appreciate some help.  Here's what I 
want to do.  I want to define a record type one of whose fields is an 
array, and I want to be able to update the array.  So the array has to be 
unique and, therefore, the record type has to be unique:

:: *A = { id :: Int
         , a  :: *{Int}
         }

In a unique array of unique arrays, I could use the replace function to 
get a unique reference to one of the arrays stored in the outer array.  My 
question is:  Is there a similar way to get a unique reference to the 
elements of a record?  The reason why I'd like to do this is that I have a 
number of nested unique references of this type.  In particular, I have 
another record type:

:: *B = { id :: Int
         , a  :: *{A}
         }

So threading my way through the reference hierarchy makes for rather 
unreadable code, and I'd like to have a reference to the array inside an 
A-record to manipulate it and later patch it back into the A-record.

Thanks,
Norbert