This is possible with atoms and refs and such, but I wonder if the use-case can't simply be handled with existing seq functions?
This is going against the grain of clojure's FP approach. Since no one's mentioned it yet, if it's possible for the caller of this function to be defined in terms of seqs, it's likely more appropriate to just use seqs? On Thu, Dec 5, 2013 at 3:50 PM, Dave Ray <dave...@gmail.com> wrote: > It's also doable with just swap!, fwiw: > > (defn make-blah [xs] > (let [a (atom [nil xs])] > (fn [] > (first (swap! a > (fn [[_ tail]] > [(first tail) (next tail)])))))) > > Dave > > > > On Thu, Dec 5, 2013 at 12:43 PM, Mark Engelberg > <mark.engelb...@gmail.com>wrote: > >> Although I think that a ref is the right tool for this purpose, for the >> sake of completeness, I'll illustrate the threadsafe way to use an atom >> here: >> >> (defn make-blah [v] >> (let [a (atom v)] >> (fn [] (let [current-val @a] >> (if (compare-and-set! a current-val (rest current-val)) >> (first current-val) >> (recur)))))) >> >> >> >> >> >> On Thu, Dec 5, 2013 at 12:35 PM, Mark Engelberg <mark.engelb...@gmail.com >> > wrote: >> >>> It's worth pointing out that if you really care about using it across >>> multiple threads, an atom really isn't the right tool for the job. You >>> should use a ref in order to place both the first and the rest into a >>> single transaction: >>> >>> (defn make-blah [v] >>> (let [a (ref v)] >>> (fn [] (dosync (let [x (first @a)] (alter a rest) x))))) >>> >>> >>> >>> On Thu, Dec 5, 2013 at 12:24 PM, David Simmons >>> <shortlypor...@gmail.com>wrote: >>> >>>> Hi Puzzler >>>>> >>>> >>>> I like the first approach you defined and it works perfectly thank you. >>>> >>>> cheers >>>> >>>> Dave >>>> >>>> -- >>>> -- >>>> 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. >>>> >>> >>> >> -- >> -- >> 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. >> > > -- > -- > 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. > -- -- 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.
