Oh okay. So if a value given to gen/return function is coming via a generator will shrink because that generator will shrink. But say (gen/return [1 2 3 4]) will never shrink because it is saying just return it as it is and never shrink this. Got it! :)
On Fri, Aug 14, 2015 at 10:34 PM, Carlo Zancanaro <carlozancan...@gmail.com> wrote: > What it means is that the value returned by gen/return can't be shrunk. > > Shrinking is done by constructing a (lazily evaluated) tree of "smaller" > forms of the same thing. So a number, let's say 4, contains a tree of > smaller numbers (0, 1, 2, and 3) which specify how to shrink it. (The tree > is constructed in an intelligent way to make shrinking more efficient than > "try everything".) When you use gen/return you don't have any of that > context, so the returned value cannot be shrunk. > > This situation is a bit more complex when you use gen/bind, though, > because the result of the gen/bind call "inherits" a shrink tree from the > generator given to gen/bind. That's why my function can shrink despite > using gen/return for its final value. The gen/return isn't shrinking, but > the gen/bind is. > > Carlo > > On 15 August 2015 at 02:49, Mayank Jain <firesof...@gmail.com> wrote: > >> Ah right! I knew I had to use gen/choose for this, >> I am still grokking bind :) >> >> Thanks for your help! >> That indeed did the trick for me :) >> >> One thing I am clear about is, >> If I use gen/return it says it'll not shrink. >> Does that mean when a test fails for a certain order, it won't try to >> shrink that order of collection? >> Because I have used a gen/return at the end of the generator? >> >> Thanks again for your help! :) >> >> On Fri, Aug 14, 2015 at 8:13 PM, Carlo Zancanaro < >> carlozancan...@gmail.com> wrote: >> >>> Hey Mayank! >>> >>> Similarly to your attempt last time, you need to use gen/bind to get >>> the result of a generator which you can then use to make a new generator. >>> >>> (defn- rand-interleave* [coll acc] >>> (if (seq coll) >>> (gen/bind (gen/choose 0 (dec (count coll))) >>> (fn [index] >>> (let [value (first (get coll index)) >>> coll (->> (update-in coll [index] next) >>> (remove empty?) >>> vec)] >>> (rand-interleave* coll (conj acc value))))) >>> (gen/return acc))) >>> >>> (defn rand-interleave [& colls] >>> (rand-interleave* (vec colls) [])) >>> >>> The (gen/choose 0 (dec (count coll))) is similar to your rand-count >>> function, then the generated number is passed to the function as result. >>> Writing it this way will shrink towards the (apply concat args) (ie. as >>> it shrinks it will move towards just concatenating the arguments). >>> >>> In terms of the recursion: this will eventually overflow the stack. I >>> don't know of a way to trampoline generators, so I don't know how to avoid >>> that. (This is a bit of a recurring problem with monadic code in Clojure, I >>> feel, as algo.monads had a similar problem last time I checked.) For the >>> moment I'm just ignoring this theoretical problem until it becomes a >>> practical problem. >>> >>> I hope that helps! >>> >>> Carlo >>> >>> On 14 August 2015 at 23:39, Mayank Jain <firesof...@gmail.com> wrote: >>> >>>> Hi Everyone, >>>> >>>> Here's the problem I am facing, >>>> I need to write a generator which takes any number of sequences, >>>> interleaves them but maintains the order within each sequence. >>>> Assume each sequence has at least one element. >>>> >>>> For example: >>>> >>>> (rand-interleave [1 2 3 4] [:a :b] [:A :B :C :D :E]) >>>>> => [:a 1 2 :b :A :B :C 3 :D 4 :E] >>>> >>>> >>>> (rand-interleave [1 2 3 4]) >>>>> => [1 2 3 4] >>>> >>>> >>>> (rand-interleave [1]) >>>>> => [1] >>>> >>>> >>>> (rand-interleave [1] [:a] [:A]) >>>>> => [:a 1 :A] >>>> >>>> >>>> I have been able to write this down as clojure functions. >>>> But I am unable to convert this into a test.check generator. >>>> >>>> Specifically: >>>> >>>> - How to pass random index count without using rand-int i.e. use >>>> gen/choose >>>> - How do I write recursive functions which play well with test.check >>>> >>>> Here's my take on it (without the generators). >>>> >>>> (defn- first-nth >>>>> "(first-nth [[1 2 3 4] [:a :b :c :d]] >>>>> 1) >>>>> => :a" >>>>> [coll n] >>>>> (first (nth coll n))) >>>> >>>> >>>> >>>> (defn- next-nth >>>>> "(next-nth [[1 2 3 4] [:a :b :c :d]] >>>>> 1) >>>>> => [[1 2 3 4] (:b :c :d)]" >>>>> [coll n] >>>>> (->> n >>>>> (nth coll) >>>>> next >>>>> (assoc coll n) >>>>> (remove nil?) >>>>> vec)) >>>> >>>> >>>> >>>> (defn- rand-count >>>>> [coll] >>>>> (rand-int (count coll))) >>>> >>>> >>>> >>>> (defn- rand-interleave* >>>>> [coll acc] >>>>> (let [n (rand-count coll)] >>>>> (if (not-empty coll) >>>>> (rand-interleave* (next-nth coll n) >>>>> (conj acc >>>>> (first-nth coll n))) >>>>> acc))) >>>> >>>> >>>> >>>> (defn rand-interleave >>>>> [& args] >>>>> ;; Make args a vector as I would like to >>>>> ;; look up elements by their index values. >>>>> (rand-interleave* (vec args) [])) >>>> >>>> >>>> Looking forward to any suggestions on how to solve it :) >>>> >>>> Thanks, >>>> Mayank. >>>> >>>> -- >>>> 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. >>> >> >> -- >> 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. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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