The decisions for volatile? vs other predicates were made at different times so I don't think there is necessarily any guiding design principle behind having one vs not having the other. I wrote the volatile addition, but I don't remember any of the details around why we included volatile? at that time.
The broader question is, do we need a predicate for every interface? Is this worth having vs just #(instance? clojure.lang.IAtom %). One reason a predicate can be useful is for portability with ClojureScript, so I think that adds a little more weight to atom? (and none for ref? or agent?). Another question is where this would be useful - what could do you envision where it's helpful to have it. If it's not common, then it's not worth having yet another function in core that needs to be loaded. And another question is how prevalent this function is "in the wild" either as a predicate or even more interestingly as something else. clojure.inspector and cider.nrepl actually have an atom? that is more of the traditional lisp/scheme sense of a non-collection. I see other impls of atom? in places like plumatic schema, taoensso encore, hara.common.checks, seesaw, and many others. (All of those impls are actually dated in that they check for the concrete class Atom rather than the interface IAtom that was introduced in 1.7.). See https://crossclj.info/clojure/atom%3F.html for more definitions. Having many existing impls of this function out there means that we either introduce warnings, or worse we actually introduce a core function that has different semantics - there are many similar functions that instead check for Atom, and some that do something entirely different. Weighing all this, I can't say that adding atom?, ref? (likely to have way more conflicts with different semantics), or agent? seems like a big win to me and is certainly not problem-free. When we added volatile?, that was not an existing overlap with many (or maybe any) existing functions out in the wild so was a little easier from that perspective. On Sunday, July 16, 2017 at 3:38:47 PM UTC-5, Shantanu Kumar wrote: > > Hi, > > Since Clojure 1.7 there's a `volatile?` predicate function, but no such > equivalent for atom/ref/agent. Can anybody explain the rationale behind the > difference? I found an old thread on a related topic (URL below) but would > like to know if there's an updated explanation. > https://groups.google.com/forum/#!topic/clojure/mIJK3x_SUyM > > > Shantanu > -- 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.
