Hello, eduction does not return a seq, or anything already "concrete" like that, rather it returns a new reducible, with the interesting property lying in the retention of the xform argument (a transducer).
This allows you, for instance, to pass around a collection with all the processing steps but the final rendering of the result (a seq? an aggregate result? a vector ? nil?) => it's up to the user of the educible. Since the educible is an unreduced form of the initial collection, then every time it will be "realized" into a concrete value, the hidden (behind the xform) collection will be traversed, and the transducer-returned reducing function called. Le mercredi 8 octobre 2014, Jason Gilman <jason.gil...@gmail.com> a écrit : > There's a few new functions that have been added with Transducers which > mostly have very clear use cases to me. What are the use cases for the new > eduction > <http://clojure.github.io/clojure/branch-master/clojure.core-api.html#clojure.core/eduction> > function? > (which looks like it was previously called iteration). The example at > http://clojure.org/transducers is informative. It looks similar to > sequence in that it produces something that is seq-able with the major > difference being that the transform is applied each time the sequence is > traversed. > > You can see the difference here in this code (This uses iteration instead > of eduction because I was on 1.7.0-alpha2) > > (def to-str-iteration > (iteration (map (fn [i] > (println "iteration" i) > (str i))) > (range 3))) > > (def to-str-seq > (sequence (map (fn [i] > (println "sequence" i) > (str i))) > (range 3))) > > (println "First iteration") > (dorun to-str-iteration) > (println "Second iteration") > (dorun to-str-iteration) > (println "First sequence") > (dorun to-str-seq) > (println "Second sequence") > (dorun to-str-seq) > > Printed: > First iteration > iteration 0 > iteration 0 > iteration 1 > iteration 2 > Second iteration > iteration 0 > iteration 0 > iteration 1 > iteration 2 > First sequence > sequence 0 > sequence 1 > sequence 2 > Second sequence > > Should we use eduction when we need side effects or reading the current > state during a transform and sequence when the transform is pure? Or is > there a subtler difference between the two that I'm missing? > > -- > 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 > <javascript:_e(%7B%7D,'cvml','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 > <javascript:_e(%7B%7D,'cvml','clojure%2bunsubscr...@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 > <javascript:_e(%7B%7D,'cvml','clojure%2bunsubscr...@googlegroups.com');>. > For more options, visit https://groups.google.com/d/optout. > -- Laurent Petit -- 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.
