What about the times when one simply must use loop/recur for performance reasons? Although, one thought I had on that was to write a functional version, and if it's a performance bottleneck, write a loop/recur version and call the latter in performance-critical areas, but also have tests that check that both versions have the same semantics.
On Sat, May 4, 2013 at 1:54 AM, Alex Baranosky < [email protected]> wrote: > I concur with Timothy's assessment. Really well stated and illustrated > use of reduce with a named reduce function. > > > On Fri, May 3, 2013 at 10:52 PM, Timothy Baldridge > <[email protected]>wrote: > >> In general, loop/recur shouldn't be considered idiomatic, IMO. Instead, >> try for a more functional style: >> >> >> due = 100 >> cards = cards.map do |card| >> card.applied_balance = max(0, due - card.balance) >> due -= card.applied_balance >> >> becomes (untested): >> >> (defn apply-balance-1 [{:keys [due] :as accum} [card-id balance]] >> (let [applied (max (- due balance))] >> (-> accum >> (assoc-in [:applied card-id] applied) >> (assoc-in [:due] due)))) >> >> >> (reduce apply-balance-1 >> {:due 100} >> {:card-id-1 4404.00 >> :card-id-2 3020.00 >> ....etc....}) >> >> Often I have found that using reduce forces me to break functions into >> several parts. If I used loop/recur, normally the function prelude, >> postlude and loop block are all smashed into a single function. With reduce >> + a do-step-1 function (as seen above) we can more easily reason about what >> is happening. The code is then easier to test as well, as we can test the >> calculations apart from the loop logic. >> >> When I'm performing Clojure code reviews, I often consider loop/recur to >> be a code smell. >> >> Timothy >> >> >> >> On Fri, May 3, 2013 at 3:53 PM, Armando Blancas <[email protected]>wrote: >> >>> On Friday, May 3, 2013 1:15:24 PM UTC-7, Robert Pitts wrote: >>>> >>>> Armando was a good citizen and sent along a plain-text version as well >>>> – https://groups.google.com/**group/clojure/msg/** >>>> 6aae8287bc55d436?dmode=source&**output=gplain&noredirect<https://groups.google.com/group/clojure/msg/6aae8287bc55d436?dmode=source&output=gplain&noredirect> >>> >>> >>> That must have been Google Groups doing the right thing... nice feature. >>> >>> -- >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to [email protected] >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> [email protected] >>> 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 [email protected]. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >> >> >> >> -- >> “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 [email protected] >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> [email protected] >> 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 [email protected]. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> >> > > -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to [email protected] > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > [email protected] > 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 [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to [email protected] Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to [email protected] 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 [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
