When I explain to new Clojurists what the ! means, I explain that it calls attention to a mutation function that is unsafe to call inside a transaction. Many programmers coming from Scheme are used to thinking of ! as meaning *anything* involving mutation, but that's not the case in the Clojure. This more subtle distinction (that it needs to be unsafe in a transaction) clarifies why swap! has an exclamation point, but ref-set does not, even though both involve mutation.
Assuming my description of Clojure's use of ! is correct (and if I'm wrong and am not thinking of some important counterexample, please let me know), then it doesn't really make sense for volatile to be called volatile!. Yes, volatiles are less safe than atoms, but the creation of the volatile itself is perfectly fine to occur in a transation. Only vswap! and vreset! require the exclamation point. I'd go one step further and question why we need new names vswap! and vreset!, when swap! and reset! are perfectly clear and sufficient. As Clojure has become increasingly interface and protocol-driven, it makes less and less sense to have a proliferation of function names for the same behavior on different underlying objects. vswap!, for example, is exactly the semantics you'd expect if you overloaded swap!, describing it as a function that can be applied to both atoms and volatiles, where volatiles are the more thread-unsafe, less atomic, alternative, because that's the nature of the underlying box. --Mark -- 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/d/optout.
