Yes, exactly. You can replicate what `def` and macros do using a regular function and `intern`.
On Sat, May 13, 2017 at 4:04 PM, Timothy Baldridge <tbaldri...@gmail.com> wrote: > Okay, so I've read these SO articles about 4 times now, and I finally > think I'm starting to understand what the `intern` solution is doing. I > would recommend this then can we simply state that: > > `(def x 42)` > > is equal to > > `(intern 'x 42)` > > Except the first is a compiler special form (and hence requires a compiler > and/or macro system) while the other is a function (and requires a > namespace system). That will probably save people a ton of reading. Like I > said, I program Clojure a lot, and it took me about 60 minutes of reading > and thinking about this code before I finally figured out what the problem > and the solution and the solution being presented. > > > On Sat, May 13, 2017 at 4:49 PM, Alan Thompson <clooj...@gmail.com> wrote: > >> I was just trying to answer a question posed by someone else, so I can't >> give details about the original motivation. I thought it was a good example >> of the capabilities of `intern` that I hadn't seen before, which could be >> useful in a dynamic case where one wanted to generate functions on the fly >> w/o using macros. >> >> A previous answer the OP was referred to >> <http://stackoverflow.com/questions/7852351/clojure-macro-to-generate-functions> >> was incomplete for the new question and I was trying to fill in the missing >> parts. >> >> >> >> On Sat, May 13, 2017 at 3:40 PM, Timothy Baldridge <tbaldri...@gmail.com> >> wrote: >> >>> Sorry, but this use of intern is a pointless. What does intern give you >>> that a let over a defn doesn't? >>> >>> On Sat, May 13, 2017 at 4:37 PM, Alan Thompson <clooj...@gmail.com> >>> wrote: >>> >>>> If anyone is interested, I cleaned up the question to (hopefully) make >>>> it clearer, as well as adding the macro-calling-a-macro solution. >>>> >>>> While some may consider it esoteric, I thought it was a good example of >>>> the power `intern` can provide, as well as a good way to avoid macros and >>>> stick to pure functions. >>>> >>>> Here is the re-worked version: http://stackoverflow.com/ques >>>> tions/43958471/how-to-create-clojure-defn-functions-automati >>>> cally-without-macros/ >>>> >>>> Alan >>>> >>>> On Thu, May 11, 2017 at 10:15 AM, Alan Thompson <clooj...@gmail.com> >>>> wrote: >>>> >>>>> Actually someone else wrote the original CLJS question (1): >>>>> http://stackoverflow.com/questions/43897632/mapped-calls-to >>>>> -clojurescript-macro >>>>> >>>>> It was marked as a duplicate of this question (2): >>>>> http://stackoverflow.com/questions/43897632/mapped-calls-to >>>>> -clojurescript-macro This one also had an answer using `intern` to >>>>> avoid the need for a macro. >>>>> >>>>> I didn't think question (1) was an exact duplicate of (2), and I >>>>> wanted to work out the details of solving (1) using `intern` instead of >>>>> macros (it seemed like a good goal at the time...). I tried to simplify >>>>> question (1) w/o the CLJS callback stuff, and may have oversimplified. >>>>> >>>>> Since question was closed as being a "duplicate" (in error, I think), >>>>> I couldn't answer there and posed the Q&A style answer separately at (3): >>>>> http://stackoverflow.com/questions/43904628/how-to-create-c >>>>> lojure-defn-functions-automatically >>>>> >>>>> The main goal I had here was simply finding a good way to avoid macros >>>>> when auto-generating functions, and to generalize/document the technique >>>>> described in (2) using `intern`. >>>>> >>>>> Alan >>>>> >>>>> P.S. Regarding (3), Joel Spolsky, creator of StackOverflow, has often >>>>> encouraged people to post both a question and its answer on the site: >>>>> https://stackoverflow.blog/2011/07/01/its-ok-to-ask-and-ans >>>>> wer-your-own-questions In fact, they even have a special button >>>>> for this purpose. >>>>> >>>>> >>>>> >>>>> On Thu, May 11, 2017 at 9:39 AM, Timothy Baldridge < >>>>> tbaldri...@gmail.com> wrote: >>>>> >>>>>> I assume this is a real problem you are encountering since you wrote >>>>>> the original Stack Overflow questions. As Dragan mentioned, this example >>>>>> doesn't warrant such a complex solution, maps and keywords *are* >>>>>> function, >>>>>> so all you really need is `foo` as a getter. Or even if they weren't >>>>>> functions you still have `(partial get foo)`. >>>>>> >>>>>> On Thu, May 11, 2017 at 10:27 AM, Alan Thompson <clooj...@gmail.com> >>>>>> wrote: >>>>>> >>>>>>> Since the original question was in CLJS, which has neither `intern` >>>>>>> nor `eval`, does that mean the macro mapping another macro approach is >>>>>>> the >>>>>>> only solution there? >>>>>>> >>>>>>> >>>>>>> On Thu, May 11, 2017 at 9:18 AM, Alan Thompson <clooj...@gmail.com> >>>>>>> wrote: >>>>>>> >>>>>>>> I like the idea of using `eval` and `memoize`. I'll have to keep >>>>>>>> that in mind. >>>>>>>> Alan >>>>>>>> >>>>>>>> On Thu, May 11, 2017 at 7:58 AM, Timothy Baldridge < >>>>>>>> tbaldri...@gmail.com> wrote: >>>>>>>> >>>>>>>>> This is a somewhat weird answer to a overcomplicated problem. As >>>>>>>>> mentioned, the data is a map to start with, and maps are functions so >>>>>>>>> treating the maps as data is probably the best approach. And like >>>>>>>>> Dragan, >>>>>>>>> I'm unsure why this example doesn't use `(data :able)`. >>>>>>>>> >>>>>>>>> When I do need to generate functions at runtime, and I can't use >>>>>>>>> macros (for the reasons mentioned), I'll either use a macro that >>>>>>>>> creates a >>>>>>>>> var, or use eval perhaps in conjunction with a memoize. I used this a >>>>>>>>> lot >>>>>>>>> in my work with JavaFx. Do some reflection, generate some code, eval >>>>>>>>> the >>>>>>>>> code and return a function, memoize that process so we can get the >>>>>>>>> generated function via name. So the interface looks like this: >>>>>>>>> >>>>>>>>> ((get-setter button :text) "hey") >>>>>>>>> >>>>>>>>> Get-setter does a ton of reflection, but calling the returned >>>>>>>>> function remains fast due to the combination of eval and memoization. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Thu, May 11, 2017 at 2:55 AM, Dragan Djuric <draga...@gmail.com >>>>>>>>> > wrote: >>>>>>>>> >>>>>>>>>> What's wrong with (foo :able) => "Adelicious!" and (:able foo) => >>>>>>>>>> "Adelicious!"? >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Thursday, May 11, 2017 at 9:20:19 AM UTC+2, Alan Thompson >>>>>>>>>> wrote: >>>>>>>>>>> >>>>>>>>>>> A recent question on StackOverflow raised the question of the >>>>>>>>>>> best way to automatically generate functions. Suppose you want to >>>>>>>>>>> automate >>>>>>>>>>> the creation of code like this: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> (def foo >>>>>>>>>>> {:able "Adelicious!" >>>>>>>>>>> :baker "Barbrallicious!" >>>>>>>>>>> :charlie "Charlizable"}) >>>>>>>>>>> (def bar >>>>>>>>>>> {:able "Apple" >>>>>>>>>>> :baker "Berry" >>>>>>>>>>> :charlie "Kumquat"}) >>>>>>>>>>> >>>>>>>>>>> (defn manual-my-foo [item] (get foo item)) >>>>>>>>>>> (defn manual-my-bar [item] (get bar item)) >>>>>>>>>>> >>>>>>>>>>> (manual-my-foo :able) => "Adelicious!" >>>>>>>>>>> (manual-my-bar :charlie) => "Kumquat" >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> You could write a macro to generate one of these at a time, but >>>>>>>>>>> you can't pass a macro to a higher-order function like `map`, so >>>>>>>>>>> while this >>>>>>>>>>> would work: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> (generate-fn :foo) ;=> creates `my-foo` w/o hand-writing it >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> this wouldn't work: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> (map generate-fn [:foo :bar :baz]) >>>>>>>>>>> >>>>>>>>>>> While one could write a 2nd macro to replace `map`, this is a >>>>>>>>>>> symptom of the "Turtles All the Way Down" problem. One workaround >>>>>>>>>>> is to >>>>>>>>>>> avoid macros altogether and use only functions to generate the >>>>>>>>>>> required >>>>>>>>>>> `my-foo` and `my-bar` functions. The trick is to make use of the >>>>>>>>>>> built-in >>>>>>>>>>> Clojure function `intern` both to save the newly generated >>>>>>>>>>> functions into >>>>>>>>>>> the global environment and to retrieve the pre-existing maps `foo` >>>>>>>>>>> and >>>>>>>>>>> `bar`. Full details are available Q&A-style at the >>>>>>>>>>> StackOverflow post >>>>>>>>>>> <http://stackoverflow.com/questions/43904628/how-to-create-clojure-defn-functions-automatically/43904717#43904717> >>>>>>>>>>> . >>>>>>>>>>> >>>>>>>>>>> Enjoy, >>>>>>>>>>> Alan >>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>> 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. >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> -- >>>>>>> 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. >>>>>> >>>>> >>>>> >>>> -- >>>> 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. >>> >> >> -- >> 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. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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