Cora (every? (fn [member] (member)) members) works fine on [constantly true & false but fails with java.lang.Boolean cannot be cast to clojure.lang.IFn on the lists I construct.
In truth, I thought all the code was working, but that turned out ot be an artifact of the test I designed. When I changed the test conditions, evaluate_and failed. On Sun, Jul 18, 2021 at 5:00 PM Cora Sutton <c...@sutton.me> wrote: > Hello again Jack, > > On Sun, Jul 18, 2021 at 6:21 PM Jack Park <jackp...@topicquests.org> > wrote: > >> (every? eval members) does not appear to work on a list of functions >> designed to evaluate to a boolean. >> > > If members is a list of functions then you would do: > > (every? (fn [member] (member)) members) > > Showing it work here: > > (every? (fn [member] (member)) [(constantly true) (constantly true)]) > ;; => true > (every? (fn [member] (member)) [(constantly true) (constantly false)]) > ;; => false > > >> That code is used in a function evaluateAnd >> >> Two simple tests >> (evaluateAnd [true true] --> true >> (evaluateAnd [true false] --> nil (why not "false" as the every? examples >> show?) >> > > In Clojure things are either "truthy" or "falsey", and the only "false" > values are false and nil so returning nil is usually fine. Everything else > is "truthy". I wouldn't worry about it returning nil since other things > were broken anyways. > > https://clojure.org/guides/learn/flow#_truth > > >> The specific code for building the list of functions is this >> >> (def x (atom [])) >> (let [result (list (ref SimpleTrue) (ref SimpleFalse))] >> (println "BAL1" result ) >> (reset! x result) >> ) >> (println "BAL2" @x ) >> >> (@x) <<<< returns the atom's value >> >> And the final println is this >> >> BAL2 (#object[clojure.lang.Ref 0x335b5620 {:status :ready, :val >> #object[ie4clj.Tests$SimpleTrue 0x6eb2384f >> ie4clj.Tests$SimpleTrue@6eb2384f]}] >> #object[clojure.lang.Ref 0x3c9c0d96 {:status :ready, :val >> #object[ie4clj.Tests$SimpleFalse 0x31dadd46 >> ie4clj.Tests$SimpleFalse@31dadd46]}]) >> >> evaluateAnd never saw the result, with this error message >> >> clojure.lang.PersistentList cannot be cast to clojure.lang.IFn >> > > Refs are the wrong thing to use here. In fact I'd stay away from atoms and > refs unless you have multiple threads that need to mutate the same values. > They're just confusing things now, I think. > > >> >> The test which fails is this >> >> (def result (evaluateAnd (buildAndList) )) <<< fails here >> (println "bar" result) >> (result) >> >> The googleverse seems to agree that there are extra parens around the >> value. Google isn't giving me an obvious way to take that value outside of >> its surrounding parens (bal2 above). >> Still looking, and hoping that solves the problem. >> Maybe there's a way to go back to buildAndList and not return the value >> with parens. >> > > I think a key thing to explain is that in Clojure generally you're not > making new types of collections. There's this famous-ish saying that > Clojure holds to pretty well: > > "It is better to have 100 functions operate on one data structure than 10 > functions on 10 data structures." > - Alan Perlis > > Most functions in the Clojure world operate on a handful of basic data > types and structures. This makes it really easy to chain and combine > functions to slice and dice data since you don't need to convert between > types. > > I don't think I've ever made a special collection type in Clojure, it's > not all that common. So I'd suggest that while you're at this point in your > journey you try to stick to the built-in Clojure collection types and use > the built-in functions to operate on them. > > To give you a little direction, instead of a Person object you could make > a hashmap like {:first-name "Jack" :last-name "Park"} and pass that > around. And then you can make a function that operates on that. > > (defn full-name > [person] > (str (get person :first-name) " " (get person :last-name))) > > And then you could expand that to maybe {:first-name "Jack" :last-name > "Park" :people-talked-to-on-mailing-list ["Cora Sutton"]} and then > operate on a collection of people like: > > (defn people-talked-to-on-mailing-list > [person all-people] > (let [people-to-find (set (get person > :people-talked-to-on-mailing-list))] > (filter (fn [p] > (people-to-find (full-name p)) > all-people)) > > (people-talked-to-on-mailing-list jack all-people) > ;; => {:first-name "Cora" :last-name "Sutton" > :people-talked-to-on-mailing-list ["Jack Park"]} > > > >> On Sun, Jul 18, 2021 at 11:23 AM Cora Sutton <c...@sutton.me> wrote: >> >>> Hi Jack! >>> >>> I could be wrong but I think this could just be: (every? eval members) >>> >>> I see a few things here that seem strange to me so I wanted to share a >>> few points that might be helpful (or might not, let me know either way) for >>> future code. >>> >>> * So typically you don't want to def or defn within another function >>> call since that will define a new value at the top level. >>> >>> (defn foo [] >>> (def bar 1) >>> (println (inc bar)) >>> >>> (foo) >>> ;; ^^ calling foo will define bar at the top level >>> >>> bar >>> ;; => 1 >>> ;; whoops, didn't mean to have that at the top level like that >>> ;; imagine if two different threads called that in parallel ::grimace:: >>> >>> Instead, you usually want to use the let function: >>> https://clojuredocs.org/clojure.core/let >>> >>> So in your code you might use this something like: >>> >>> (let [result (atom true)] >>> ....) >>> >>> The error you're seeing is from the (defn result ...) in your code, >>> you're missing the argument vector [] after result -- so it would look >>> like (defn result [] (atom true)) -- but you really don't want to defn >>> like that, I think. >>> >>> * To update an atom's value you don't want to assign like that, you want >>> to use swap! https://clojuredocs.org/clojure.core/swap! >>> >>> (swap! f >>> (fn [cur-val new-val] (and cur-val new-val)) >>> (eval member)) >>> >>> * You probably don't want to use an atom here. Atoms are usually for >>> data that you intend to have multiple threads accessing. In this case it's >>> just a value that changes during a single thread's execution here. >>> >>> How else could you solve this if not for the very convenient every? >>> function? There are a bunch of ways! Here are a few, with things written >>> out pretty explicitly so they're more clear. >>> >>> loop/recur: >>> >>> (loop [result true >>> remaining-members members] >>> (let [member (first remaining-members) >>> remaining-members (rest members) >>> new-result (eval member)] >>> (if new-result >>> (recur true remaining-members) >>> false))) >>> >>> reduce v1: >>> >>> (reduce (fn [result member] >>> (and result >>> (eval member))) >>> true >>> members) >>> >>> reduce v2.0, that will now stop iterating once one of the members evals >>> to false: >>> >>> (reduce (fn [_ member] >>> (or (eval member) >>> (reduced false))) >>> true >>> members) >>> >>> My point with sharing these is that in clojure usually the best way to >>> solve these problems is to pass new values to the next iteration while >>> accumulating a result instead of changing a variable on each iteration. Or >>> to use one of these sweet built-in functions. >>> >>> Does that make sense? >>> >>> * I thiiiiiiink you might not mean eval but I'm interested in what kind >>> of problem you're solving! :) >>> >>> Hope that helps! >>> Cora >>> >>> On Sun, Jul 18, 2021 at 12:41 PM Jack Park <jackp...@topicquests.org> >>> wrote: >>> >>>> I have a class which treats a sequence as a conjunctive list of objects >>>> which, when evaluated, return a boolean. It is an attempt to use doseq to >>>> walk along that list, evaluating each entry, and anding that result with >>>> boolean atom. It fails. A sketch of the code is this - taken from the error >>>> message: >>>> >>>> inside (defn AndList... >>>> >>>> (reify >>>> ie4clj.api.Inferrable >>>> (defn evalMembers >>>> [members] >>>> (defn result (atom true)) >>>> (doseq [x members] >>>> (result = (and result (eval x)))) >>>> (println (clojure.core/deref result)) >>>> (result))) - *failed: vector? at: [:fn-tail :arity-1 :params] >>>> spec: :clojure.core.specs.alpha/param-list* >>>> >>>> It could be that my Java background is clouding my use of clojure. Any >>>> comments will be appreciated. >>>> >>>> Thanks >>>> Jack >>>> >>>> -- >>>> 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. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/clojure/f67cfcd0-8e1e-4780-bc00-f6993979e7afn%40googlegroups.com >>>> <https://groups.google.com/d/msgid/clojure/f67cfcd0-8e1e-4780-bc00-f6993979e7afn%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> 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. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/clojure/CAMZDCY3BWybiXzgoYaKK958z%2BWqTKf0o_5p9fq-huwutco9onw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/clojure/CAMZDCY3BWybiXzgoYaKK958z%2BWqTKf0o_5p9fq-huwutco9onw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> 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. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/clojure/CAH6s0fwv-rKrWnXji_r4scaX9_jtAi1CRUWGLLNRj7iZtme4UA%40mail.gmail.com >> <https://groups.google.com/d/msgid/clojure/CAH6s0fwv-rKrWnXji_r4scaX9_jtAi1CRUWGLLNRj7iZtme4UA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > > On Sun, Jul 18, 2021 at 6:21 PM Jack Park <jackp...@topicquests.org> > wrote: > >> (every? eval members) does not appear to work on a list of functions >> designed to evaluate to a boolean. >> >> That code is used in a function evaluateAnd >> >> Two simple tests >> (evaluateAnd [true true] --> true >> (evaluateAnd [true false] --> nil (why not "false" as the every? examples >> show?) >> >> The specific code for building the list of functions is this >> >> (def x (atom [])) >> (let [result (list (ref SimpleTrue) (ref SimpleFalse))] >> (println "BAL1" result ) >> (reset! x result) >> ) >> (println "BAL2" @x ) >> >> (@x) <<<< returns the atom's value >> >> And the final println is this >> >> BAL2 (#object[clojure.lang.Ref 0x335b5620 {:status :ready, :val >> #object[ie4clj.Tests$SimpleTrue 0x6eb2384f >> ie4clj.Tests$SimpleTrue@6eb2384f]}] >> #object[clojure.lang.Ref 0x3c9c0d96 {:status :ready, :val >> #object[ie4clj.Tests$SimpleFalse 0x31dadd46 >> ie4clj.Tests$SimpleFalse@31dadd46]}]) >> >> evaluateAnd never saw the result, with this error message >> >> clojure.lang.PersistentList cannot be cast to clojure.lang.IFn >> >> The test which fails is this >> >> (def result (evaluateAnd (buildAndList) )) <<< fails here >> (println "bar" result) >> (result) >> >> The googleverse seems to agree that there are extra parens around the >> value. Google isn't giving me an obvious way to take that value outside of >> its surrounding parens (bal2 above). >> Still looking, and hoping that solves the problem. >> Maybe there's a way to go back to buildAndList and not return the value >> with parens. >> >> On Sun, Jul 18, 2021 at 11:23 AM Cora Sutton <c...@sutton.me> wrote: >> >>> Hi Jack! >>> >>> I could be wrong but I think this could just be: (every? eval members) >>> >>> I see a few things here that seem strange to me so I wanted to share a >>> few points that might be helpful (or might not, let me know either way) for >>> future code. >>> >>> * So typically you don't want to def or defn within another function >>> call since that will define a new value at the top level. >>> >>> (defn foo [] >>> (def bar 1) >>> (println (inc bar)) >>> >>> (foo) >>> ;; ^^ calling foo will define bar at the top level >>> >>> bar >>> ;; => 1 >>> ;; whoops, didn't mean to have that at the top level like that >>> ;; imagine if two different threads called that in parallel ::grimace:: >>> >>> Instead, you usually want to use the let function: >>> https://clojuredocs.org/clojure.core/let >>> >>> So in your code you might use this something like: >>> >>> (let [result (atom true)] >>> ....) >>> >>> The error you're seeing is from the (defn result ...) in your code, >>> you're missing the argument vector [] after result -- so it would look >>> like (defn result [] (atom true)) -- but you really don't want to defn >>> like that, I think. >>> >>> * To update an atom's value you don't want to assign like that, you want >>> to use swap! https://clojuredocs.org/clojure.core/swap! >>> >>> (swap! f >>> (fn [cur-val new-val] (and cur-val new-val)) >>> (eval member)) >>> >>> * You probably don't want to use an atom here. Atoms are usually for >>> data that you intend to have multiple threads accessing. In this case it's >>> just a value that changes during a single thread's execution here. >>> >>> How else could you solve this if not for the very convenient every? >>> function? There are a bunch of ways! Here are a few, with things written >>> out pretty explicitly so they're more clear. >>> >>> loop/recur: >>> >>> (loop [result true >>> remaining-members members] >>> (let [member (first remaining-members) >>> remaining-members (rest members) >>> new-result (eval member)] >>> (if new-result >>> (recur true remaining-members) >>> false))) >>> >>> reduce v1: >>> >>> (reduce (fn [result member] >>> (and result >>> (eval member))) >>> true >>> members) >>> >>> reduce v2.0, that will now stop iterating once one of the members evals >>> to false: >>> >>> (reduce (fn [_ member] >>> (or (eval member) >>> (reduced false))) >>> true >>> members) >>> >>> My point with sharing these is that in clojure usually the best way to >>> solve these problems is to pass new values to the next iteration while >>> accumulating a result instead of changing a variable on each iteration. Or >>> to use one of these sweet built-in functions. >>> >>> Does that make sense? >>> >>> * I thiiiiiiink you might not mean eval but I'm interested in what kind >>> of problem you're solving! :) >>> >>> Hope that helps! >>> Cora >>> >>> On Sun, Jul 18, 2021 at 12:41 PM Jack Park <jackp...@topicquests.org> >>> wrote: >>> >>>> I have a class which treats a sequence as a conjunctive list of objects >>>> which, when evaluated, return a boolean. It is an attempt to use doseq to >>>> walk along that list, evaluating each entry, and anding that result with >>>> boolean atom. It fails. A sketch of the code is this - taken from the error >>>> message: >>>> >>>> inside (defn AndList... >>>> >>>> (reify >>>> ie4clj.api.Inferrable >>>> (defn evalMembers >>>> [members] >>>> (defn result (atom true)) >>>> (doseq [x members] >>>> (result = (and result (eval x)))) >>>> (println (clojure.core/deref result)) >>>> (result))) - *failed: vector? at: [:fn-tail :arity-1 :params] >>>> spec: :clojure.core.specs.alpha/param-list* >>>> >>>> It could be that my Java background is clouding my use of clojure. Any >>>> comments will be appreciated. >>>> >>>> Thanks >>>> Jack >>>> >>>> -- >>>> 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. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/clojure/f67cfcd0-8e1e-4780-bc00-f6993979e7afn%40googlegroups.com >>>> <https://groups.google.com/d/msgid/clojure/f67cfcd0-8e1e-4780-bc00-f6993979e7afn%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> 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. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/clojure/CAMZDCY3BWybiXzgoYaKK958z%2BWqTKf0o_5p9fq-huwutco9onw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/clojure/CAMZDCY3BWybiXzgoYaKK958z%2BWqTKf0o_5p9fq-huwutco9onw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> 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. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/clojure/CAH6s0fwv-rKrWnXji_r4scaX9_jtAi1CRUWGLLNRj7iZtme4UA%40mail.gmail.com >> <https://groups.google.com/d/msgid/clojure/CAH6s0fwv-rKrWnXji_r4scaX9_jtAi1CRUWGLLNRj7iZtme4UA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/clojure/CAMZDCY1wvo_N32dKV1g-9cZAmTbZUO5bRAXDGkdHm-7_VD_-Rg%40mail.gmail.com > <https://groups.google.com/d/msgid/clojure/CAMZDCY1wvo_N32dKV1g-9cZAmTbZUO5bRAXDGkdHm-7_VD_-Rg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/CAH6s0fyc%2BctV%2B1OgzWRYLsWevL97ouVkS1FGf0uGFtTcznRjUg%40mail.gmail.com.
