Thanks !
 
Now, a small follow-up question: if I subsequently test 2 Instances whether they were instantiated with the same Attributes value, as in
 
test (Instance a1 _) (Instance a2 _) = (a1==a2)
 
will this be implemented efficiently ? I.e. will it check first whether the pointers happen to be the same, and only then do a full Eq comparison ?
 
Cheers
Frank
----- Original Message -----
From: Simon Peyton-Jones
To: Frank Dellaert ; Haskell@haskell.org
Sent: Monday, December 17, 2001 10:24 AM
Subject: RE: space efficiency question

Now: if I have a couple of thousand of these Instances, created with the same Attributes value, as in:
 
a = Attributes ["a","bc"]
i0000 = Instance a [1,2]
i0001 = Instance a [1,1]
...
i7896 = Instance a [2,1]
 
can I be assured that there are not thousands of actual copies of a but that they simply have a pointer to a ? I'm interested in the answer for both ghc (compiled/interpreted) as interpreted Hugs. 
Yes for GHC: you'll only get one copy of 'a'.
 
Simon