Re: Idiomatic way to return a single value from an async function
You could do both: Make the channel optional. If it's provided, use that and return it. If it's not provided, create a new one and use and return that. This way the caller gets to decide which they wish to use based on who the owner of the channel should be or if the channel should be reused elsewhere. For example, for a once-off call, creating s new channel may make more sense but if the function is called frequently it might make more sense to reuse one channel, especially if this channel is used with other plumbing like pub/sub or mult which you would otherwise need to set up every time. On Mon, 10 Nov 2014 17:42 Mike Haney txmikes...@gmail.com wrote: Eric Normand has an interesting article on this here: http://www.lispcast.com/core-async-code-style -- 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. -- 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.
Re: Idiomatic way to return a single value from an async function
+1, this is mostly what we resort to. (defn some-async-func [param-a param-b [out-chan]] (let [ch (or out-chan (chan)] ... ) 2014-11-11 8:53 GMT+00:00 Daniel Kersten dkers...@gmail.com: You could do both: Make the channel optional. If it's provided, use that and return it. If it's not provided, create a new one and use and return that. This way the caller gets to decide which they wish to use based on who the owner of the channel should be or if the channel should be reused elsewhere. For example, for a once-off call, creating s new channel may make more sense but if the function is called frequently it might make more sense to reuse one channel, especially if this channel is used with other plumbing like pub/sub or mult which you would otherwise need to set up every time. On Mon, 10 Nov 2014 17:42 Mike Haney txmikes...@gmail.com wrote: Eric Normand has an interesting article on this here: http://www.lispcast.com/core-async-code-style -- 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. -- 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. -- László Török Checkout justonemorepoint.com - Know your true value -- 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.
Re: Idiomatic way to return a single value from an async function
Hey, what is your definition of an async function in Clojure? I imagine something something that starts a (go ...), if appropriate you can use the result of (go ...) as the result of the function since that is a channel that will receive the return value of the go block when it dies. (defn start-async [] (go (! (async/timeout 1000)) :done)) (let [c (start-async)] (prn (!! c))) Other than it is highly dependent on the function you are writing. Sometimes it will be required to take an external channel, sometimes it will be useless. Usually depends on the types of coordination required between the different parts. There is no universally correct way. Just my 2 cents, /thomas On Monday, November 10, 2014 5:30:41 PM UTC+1, Alexander Kiel wrote: Hi, what is the most idiomatic way to return a single value from an async function in Clojure? A: return a channel which conveys the result later; also closes the channel (defn f [x] (let [c (chan)] ; put result onto c and close c later c)) B: take a channel onto which the result is put later; do not close that channel; return nil immediately (defn f [x c] ; put result onto and close c later nil) Variant A has the advantage that it needs one function argument less than variant B. It's also better usable in higher order functions like map. Variant A is also more easy to use if you need to create a channel anyway. Variant A has the disadvantage of creating a new channel each time the async function is called. According my measurements using criterium 0.4.3, clojure 1.6.0 and core.async 0.1.346.0-17112a-alpha, the runtime cost of creating a channel is about 8 times more expensive as creating a single object. Variant B has the advantage to not create a channel on every call. You can supply the same channel many times to the function. On the other hand, the results of multiple calls to f are not likely to arrive on that single channel in call order. If you have such an ordering requirement, you have to create a single channel for each function call anyway. Variant B has the disadvantage that it requires one function argument more than variant A. As a consequence, you can't simply map such a function over a list of inputs. Variant A seems to be the winner. But I ask specially because pipeline-async https://clojure.github.io/core.async/#clojure.core.async/pipeline-async uses variant B. What do you think? Alex -- 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.
Re: Idiomatic way to return a single value from an async function
Similarly, but I would be explicit about the different arities, to avoid the intermediate sequence created by [arg [option]] and to get errors if there are too many arguments. (defn foo ([input] (foo input (chan 1)) ([input ch] ... do something and put to ch ...)) If your function can produce multiple outputs, you can `close!` the channel to signal it is finished, which is what `pipeline-async` expects. –S -- 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.
Idiomatic way to return a single value from an async function
Hi, what is the most idiomatic way to return a single value from an async function in Clojure? A: return a channel which conveys the result later; also closes the channel (defn f [x] (let [c (chan)] ; put result onto c and close c later c)) B: take a channel onto which the result is put later; do not close that channel; return nil immediately (defn f [x c] ; put result onto and close c later nil) Variant A has the advantage that it needs one function argument less than variant B. It's also better usable in higher order functions like map. Variant A is also more easy to use if you need to create a channel anyway. Variant A has the disadvantage of creating a new channel each time the async function is called. According my measurements using criterium 0.4.3, clojure 1.6.0 and core.async 0.1.346.0-17112a-alpha, the runtime cost of creating a channel is about 8 times more expensive as creating a single object. Variant B has the advantage to not create a channel on every call. You can supply the same channel many times to the function. On the other hand, the results of multiple calls to f are not likely to arrive on that single channel in call order. If you have such an ordering requirement, you have to create a single channel for each function call anyway. Variant B has the disadvantage that it requires one function argument more than variant A. As a consequence, you can't simply map such a function over a list of inputs. Variant A seems to be the winner. But I ask specially because pipeline-async https://clojure.github.io/core.async/#clojure.core.async/pipeline-async uses variant B. What do you think? Alex -- 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.
Idiomatic way to return a single value from an async function
Eric Normand has an interesting article on this here: http://www.lispcast.com/core-async-code-style -- 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.
