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-automat >> ically-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 - 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