The go block itself (and thus any call to walker) returns a channel. This value is indeed thrown away; its utility lies entirely in the fact that the caller had to wait for it. All of the actual values from the tree are written to the supplied channel 'ch', and the ultimate caller of this function will have to take them from there.
I am stupid and recursion is clearly beyond my intellect. Martin Trojer has a great blog post here which I learned a lot from but I don't understand why the final example works: http://martintrojer.github.io/clojure/2013/07/17/non-tailrecursive-functions-in-coreasync/ He offers this as an example of recursively walking a binary search tree: (defn walk [tree ch] (letfn [(walker [t] (go (when t (walker (:left t)) (>! ch (:value t)) (walker (:right t)))))] (go (<! (walker tree)) (close! ch)))) and then he writes: "This looks promising, but the results in the channel can be in any order (since there are no order guarantees in the scheduling of go processes) – this also means that some of the values might be missing since the “top” go process can be scheduled before a child one. We need a little bit more synchronisation to arrive at a working solution." and then offers this as the final working example: (defn walk [tree ch] (letfn [(walker [t] (go (when t (<! (walker (:left t))) (>! ch (:value t)) (<! (walker (:right t))))))] (go (<! (walker tree)) (close! ch)))) I am confused what this line does: (<! (walker (:left t))) It looks like we are pulling a value off channel that's returned from that call to walker? But why? We seem to be throwing this value away? I don't see it being stored anywhere. How does this give us synchronization? -- -- 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.
