Hi again Andrey! Not to drag this out, but you seem to have missed my main point, which also means that I failed to make it. :-)
Understanding how comp works and seeing the function, lens, for defining a cat's lens, it is not at all obvious how a cat's lens works. On the other hand, the dewdrop lens constructor simply creates a record. And a quick review of the code for dewdrop's ladd shows clearly how dewdrop lenses are composed. Dewdrop then allows a developer to leverage ones own intuition. So a developer may quickly pick up on how to use cat, but must trust that any bugs lie in that developer's own code. Or perhaps take time to learn how a cat lens works at 3 AM when the servers are crashing. Not likely, I'll grant you. But I prefer not to have to trust in magic when I have a choice. Too often such magic has a domain that is a bit different than what I was expecting. Not understanding how something works, I usually lack a similar understanding as to when I should or should not use it. Keep in mind also that clojure has a lot more than just functions, and composition applies to a lot more things than just functions as well. Indeed, my favorite technique is compositions of bags of properties serving in place of objects. So learning how to call a method to compose two records is hardly a stretch and well worth the price for being able to understand what is going on internally. On Friday, January 1, 2016 at 3:35:29 PM UTC-5, Andrey Antukh wrote: > > > > On Fri, Jan 1, 2016 at 9:53 PM, William la Forge <lafo...@gmail.com > <javascript:>> wrote: > >> Andrey, >> >> This is where I have a problem. Ii could have implemented dewdrop lenses >> as functions that could be composed. But the code would be harder to >> understand and possibly be slower. I just do not see the point. >> > > I agree with your main argument, but I don't know how using records makes > thinks more easy understandable in this concrete case and how using > functions over records will make code slower. Transducers has a performance > improvements over classical transformation compositions, and in this case, > the cats lenses leverage the same technique. > > >> >> Implementing dewdrop lenses as records makes it dirt simple for anyone to >> create more kinds of lenses. And the ladd function to create a new record >> with the composed getter and setter functions is pretty clean as well. >> > > Yes but it implies more api to know, that is not bad but if you limit the > set of new api that one should learn/use, will contribute to more familiar > and easy api. Adding new api also implies more time to understand it and > remember when it should be used. > > >> >> Isn't it more important to have code you can analyze easily, and which >> even a novice clojurist like myself can embrace and enhance a whole lot >> more important than being able to say that we can use comp to compose these >> lenses??? >> > > Yes, I agree with you, the code readability is very very important. But > this concrete case I don't found big differences in code readability: > > ;; dewdrop > (defn key-lens [k] > (lens. > (fn [d] (get d k)) > (fn [d v] (assoc d k v)))) > > ;; cats > (defn key > [k] > (lens > (fn [s] (get s k)) > (fn [s f] (update s k f)))) > > The code is mostly the same... > > >> I see good engineering as leveraging computer science so the programming >> grunts can make effective use of it. Programming is real grunt work, after >> all. No matter how much you dress it up, we all needs must get our hands >> dirty and put our backs into it. >> > > My two cents. > Andrey > >> >> Bill >> >> On Friday, January 1, 2016 at 9:09:08 AM UTC-5, Andrey Antukh wrote: >>> >>> Hi! >>> >>> I have read the readme and I don't found a big evidence of something >>> wrong so, nice work! >>> Furthermore, do you know about https://github.com/funcool/cats ? It has >>> a lens and traversable implementation for clj/cljs. You can read the >>> related documentation here: http://funcool.github.io/cats/latest/#lens >>> . >>> >>> You can found that lenses, using cats approach, are working just like >>> transducers (function composition), you do not need any special function >>> for combine lenses, just use comp. One of the readme examples (from >>> your repository) that combines two lenses, in cats can be written in this >>> way: >>> >>> (require '[cats.labs.lens :as l]) >>> (def xy-lens (comp (l/key :x) (l/key :y)) >>> ;; Or just use (l/in [:x :y]) >>> >>> (l/focus xy-lens {:x {:y 1}}) >>> ;; => 1 >>> (l/over xy-lens inc {:x {:y 1}}) >>> ;; => {:x {:y 2}} >>> >>> Happy new year! >>> Andrey >>> >>> On Fri, Jan 1, 2016 at 2:54 PM, William la Forge <lafo...@gmail.com> >>> wrote: >>> >>>> I've been looking at lenses and while it looks pretty simple and very >>>> useful, I had a hard time getting it. So I came up with my own take on >>>> lenses. https://github.com/laforge49/dewdrop#readme >>>> >>>> So perhaps I still do not understand lenses and what I've done is >>>> wrong. Or perhaps having been through the exercise I'm now getting it and >>>> what I've done is no simpler than what everyone else has done. Or perhaps >>>> I've just described things with fewer technical terms. >>>> >>>> So I'd appreciate it if you would review this very short document and >>>> tell me what I don't understand. Or that I've actually done something >>>> worthwhile with lenses??? >>>> >>>> Thanks! >>>> Bill >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To post to this group, send email to clo...@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+u...@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+u...@googlegroups.com. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> >>> >>> >>> -- >>> Andrey Antukh - Андрей Антух - <ni...@niwi.nz> >>> http://www.niwi.nz >>> https://github.com/niwinz >>> >> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to clo...@googlegroups.com >> <javascript:> >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> clojure+u...@googlegroups.com <javascript:> >> 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+u...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Andrey Antukh - Андрей Антух - <ni...@niwi.nz <javascript:>> > http://www.niwi.nz > https://github.com/niwinz > -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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