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Isn't Gemini the name for Andrew's specific pattern, rather than "a replicator based on a universal constructor"? Keiji 20:17, 19 May 2010 (UTC)

Yes, it is. Replicators based on universal constructors can use much more diverse methods, such as true von Neumannesque replication. --Calcyman 18:34, 20 May 2010 (UTC)

Perhaps my understanding is flawed here. I was under the impression that a replicator would need to create at least two coincident copies of itself, but Gemini creates one copy of itself while deleting the other (I also thought that it didn't copy its tape, but rather inserted it into the new copy of its circuitry - I haven't run it through a complete period, so I haven't yet seen quite how it works). would it not be equivalent to say that a glider creates itself and destroys the previous pattern every 4 generations? I think this page needs a clearer definition of replicator at the very least. I'll remove the "offending line" until this problem is resolved.
~Sokwe 20:58, 20 May 2010 (UTC)

The confusion may arise from the fact that we use 'Replicator' in two different (but related) ways. The first definition of 'replicator', which is probably what Sokwe is using, is a pattern equivalent to HighLife's replicator -- a pattern that generates two copies of itself. However, I'm using the second definition, which is 'any pattern that constructs itself, directed by the contents of a memory tape'. The second definition pre-dates the first by about 40 years, being devised by von Neumann as he developed his cellular automaton. --Calcyman 06:27, 21 May 2010 (UTC)
I think I see what you mean, but I suppose the von Neumann definition would not include replicators such as the one in Highlife (because they don't use the contents of a memory tape to construct themselves). Personally, I think the definition I described earlier is the most appropriate for the article, and perhaps somewhat easier to understand (although the current article doesn't state it very clearly). The article should probably also mention the von Neumann definition to differentiate it from the definition we are currently using.
~Sokwe 06:54, 22 May 2010 (UTC)
Sorry to butt in, but maybe the definition:
Anything that fits into either of the above definitions
would work better
Dictionaries seem to consider duplicate and replicate to be the same, but there must be a reason for there being two words. Maybe Latin and Saxon ancestries? My impresion is that duplicate means an exact copy, perhaps part of the same batch, or, maybe subsequently constructed from the same pattern. A replica, on the other hand, only has to be similar, perhaps as a result of trying to reconstruct the original at a later date, or by a different artisan.
Von Neumann was reportedly concerned by the difference between crystal growth and cell growth, especially sexual reproduction in which the new copy might resemble identically neither of the parents; supposedly that is why he required his reproducing automaton to have a Turing machine among its components. It would seem that the current crop of replicators work from an instruction tape á la von Neumann, even if they don't have the ability to change tapes or generate a novel tape. An intermediate situation, apparently.
The stem of the word duplicate means 'two', and thus to duplicate something is to make a (second) copy, resulting in two copies thereof. Replicate, on the other hand, does not specify the number of copies, so is a more general term. Calcyman 10:40, 23 June 2010 (UTC)