I'm not sure I've ever addressed this publicly, so I assume now's as good a time as ever.
The reason the go block stops at function boundaries, is that changing a function to be "async" changes it return type. With code transforms like these a function that performs a parking take on a channel no longer returns a object, it returns a "async object" that eventually returns an object. Notice the difference here: (fn [c] (<!! c)) (fn [c] (go (<! c)) Adding the "go" to the function (which is required to kick off the transformation) changes the return type to being a channel of objects instead of a single object. This is surfaced in other languages as well that support parking behavior. Performing an async/await operation in C# for example changes the type from "Object" to "Task<Object>". In essence, parking is infectious. Any function that calls an async function must itself either become blocking or parking. For example, for this code to work: (go (vec (map <! [c1 c2 c3 c4]))) You would have to transform all the code in map, persistent vectors, seqs and a few other bits of code. Now there are some languages/libraries that support this behavior on the JVM, two are Erjang and Pulsar. Both of these provide this functionality via whole program code transformation. That is to say they perform async/go-like transforms to all the code in the JVM, or at least all the code that interfaces with async code. I consider this a valid approach, but it is rather invasive. As such, we made a design decision early on in the development of core.async to only perform local transformation. Hopefully that provides some context. Timothy On Thu, Aug 25, 2016 at 5:29 PM, Kevin Downey <redc...@gmail.com> wrote: > The analysis for the go macro to determine that the fn never escapes the > go block is not something core.async does. Because of that functions are > sort of a black box to the transforms the go macro does. > > http://dev.clojure.org/jira/browse/ASYNC-93 is a declined issue > regarding this. http://dev.clojure.org/jira/browse/ASYNC-57 is another > similar declined issue. > > On 08/25/2016 04:21 PM, hiskennyness wrote: > > I am getting an error about >! not being in a go block with this code: > > > > | > > (go-loop [state :nl > > column 0 > > last-ws nil > > buff ""] > > (let [line-out(fn [c b] > > (>!out(apply str b (repeat (-col-width (count > > b))\space))))] > > (cond > > (>=column col-width) > > (condp =state > > :ws (do > > (line-out\|buff) > > (recur :nl 0nil"")) > > ..etc etc > > | > > > > I just changed the line-out call to just do... > > > > | > > (>!out-chan buff) > > | > > > > ...and it worked fine. > > > > So the failing code is both dynamically and lexically within the scope > > of the go-loop --- is that supposed to be that way? Or am I completely > > missing something? > > > > -kt > > > > -- > > 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 > > <mailto:clojure+unsubscr...@googlegroups.com>. > > For more options, visit https://groups.google.com/d/optout. > > > -- > And what is good, Phaedrus, > And what is not good— > Need we ask anyone to tell us these things? > > -- > 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. > -- “One of the main causes of the fall of the Roman Empire was that–lacking zero–they had no way to indicate successful termination of their C programs.” (Robert Firth) -- 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.
