Hi John,
reduced really just wraps a value in a special container; nothing magical. All it does is signal to reduce to stop. reduce knows to stop by checking with reduced?. reduced? is otherwise extremely narrow-use: it's basically only useful if you're trying to write something like reduce but different yourself. lvh On Tue, Apr 25, 2017 at 2:34 PM, John Gabriele <jmg3...@gmail.com> wrote: > Just recently stumbled upon `reduced` and `reduced?`. It seems rather > magical... how does the outer `reduce` (or `reductions`) know to stop? That > is, how does the function which is being called (`reduced`) affect the > function that's calling it (below, `reductions`)? : > > ~~~clojure > (defn main > [] > (let [res (reductions (fn [accum x] > (if (< accum 100) > (+ accum x) > (reduced [x accum]))) > (range))] > (prn res) > (prn (reduced? res)) ;=> false > (prn (reduced? (last res))))) ;=> false --- why isn't this `true`? > ~~~ > > Also, what's the use of `reduced?`, and on what in the above snippet would > I call it to return true? > > -- > 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.
