Title: Message
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No,
GHC doesn't test pointer equality first. It's unsound
to
do so,
since it might turn bottom into non-bottom, or remove
`seq`
calls that kill space leaks.
S
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 -----
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
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