Thomas Conway wrote:
On 10/4/07, Jules Bean <[EMAIL PROTECTED]> wrote:
...and indeed it can't be done, except by the naive brute-force method
of comparing every subtree, possibly optimised by cryptographically
hashing a representation of every subtree, since sharing isn't an
observable property.
At least one Prolog implementation (I forget which, I'm sorry), had a
[de]serialisation library which used a hash-consing approach.
Basically, it did its serialization using a post-order traversal and
emitted references to previous values when the same value had already
been emitted. Not rocket science. Actually, I've heard a Prolog guy -
Bart Demoen - talk about doing pretty much this during GC to improve
sharing.
Not rocket science at all, but relatively expensive. A time/space
tradeoff. And these days, with memory and disks feeling cheap, most
people want to trade time for space, not the other way around.
Not everyone, of course.
Jules
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