Hi Paul, there is a rich history of people extending the thread macros. For things in core, check out some of the other threading operators: as->, cond->, some-> etc as they handle more of your cases below. This is a good overview of what they do:
http://clojure.org/guides/threading_macros Additionally, there are a bunch of libraries that provide other variants like synthread <https://github.com/LonoCloud/synthread>, swiss-arrows <https://github.com/rplevy/swiss-arrows>, and even core.incubator <https://github.com/clojure/core.incubator>. On Wednesday, September 28, 2016 at 9:31:37 AM UTC-5, p...@pwjw.com wrote: > > Hi. > > I'm new to clojure, and it is quite lovely. The threading model is great, > the emacs integration is super, and the tasteful lisp extensions are good. > A very nice programming environment all around. > > But as I write more code I find a couple of structures I'm using a lot > which seem related to me not knowing idioms for a couple of uses cases. So > thought I'd ask and see if you have any suggestions. > > Apologies if this is covered elsewhere. And if I should read some existing > documentation I didn't find, I apologize for missing it. And thanks in > advance for your time reading! > > First the thrush operators (-> and ->>) are super handy. But I find myself > needing to 'move' arguments every now and then. So I get code which looks > like > > (->> blah > (do-this) > (do-that arg) > ((fn [s] (rearrange arg s arg)))) > > quite a lot.The alternate is a big nested let like > > (let [ first (blah) > second (do-this first) > ... > result (wrap-it-up fourteenth) ] > result) > > for sort of sequential application where arguments fall in different > 'spots'. So I sort of find myself wanting to write a 'positional-thrush' > macro like > > (-%> blah > (do-this %) > (do-that arg %) > (do-the-other a1 % a2)) > > where % is replaced with the output of the prior. But no such operator > exists as far as I can see. So either I've had a good idea (which is > unlikely since I'm super new to the language) or there's some other idiom > you all use for this pattern which I've missed. > > The second is smaller, but is more a question. clojure.test seems to only > have 'is' so for things like equality I end up writing (is (= (...) (...))) > a lot. Or to test if an exception is thrown (is (thrown? ...)). That's OK, > but I'm wondering what led to that decision rather than having is-eq and > is-thrown and so on (considering the core language has shortcuts like when > and unless and if-not so the compound macros seem idiomatic). > > The last is sort of related to the first. Sometimes I'm assembling a data > structure in a set of operators and I write them with a let or a -> and > half way through I have an error condition I want to check. In a mutable > procedural language you would do something like > > x = blah > y = bim > if (! (condition (y))) throw "y doesn't meet condition" > z = blob > > I don't see a good idiom for this. I have to split and nest lets for > instance > > (let [x (blah) y (bim) ] > (if (condition (y)) (throw ...) > (let [ z (blob) ] > )) > > which seems a bit ugly. I sort of want a let-with-test or a > thrush-with-test so something which looks like > > (-%?> (init) > (operator-1 %) (post-condition) > (operator-2 %) (post-condition) ) > > where if I don't have a post condition I could just use 'true'. Then this > expands to doing a quick '(if (not (postcondition (intermedia-result)))) > throw...) > > but that's a crazy thing to want. So curious how you all tackle this. > > Thank you all for your consideration. And apologies again if this is > covered elsewhere or I should have asked in a different forum. > > Best, > > Paul > -- 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.
