On Sat, Jun 29, 2013 at 6:06 PM, Cedric Greevey <cgree...@gmail.com> wrote:
> Who said swap *was* CAS, rather than was implemented *in terms of* CAS? In > any event, your claim that "no comparison is done unless it's done in the > supplied function" is just plain wrong. Comparison *is* done, outside that > function, to make sure the atom wasn't changed by another thread while the > function was executing. > "swap! is for "CAS"" The claim here is clearly not that swap! is implemented in terms of CAS (which would be very unenlightening, since the question was about the distinction between swap! and reset!, which can *also* be implemented in terms of CAS). I admit it would have been more careful of me to say that the semantics of swap! are such that whether or not any comparison is done is an implementation detail; those semantics (which are that swap! "[a]tomically swaps the value of atom to be: (apply f current-value-of-atom args)" don't specify a comparison, which is not the case with CAS. (reset! *isn't* implemented in terms of swap! or CAS, but it *could* be, as far as the semantics are concerned; if it were, I think it would still be right to say that reset! conceptually doesn't do a comparison against anything, even though, again, as an implementation detail, it could.) Or just look at the source for clojure.lang.Atom.swap(): > IOW, "the first 100 lines of Atom.java contain all the answers"? -- Ben Wolfson "Human kind has used its intelligence to vary the flavour of drinks, which may be sweet, aromatic, fermented or spirit-based. ... Family and social life also offer numerous other occasions to consume drinks for pleasure." [Larousse, "Drink" entry] -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
