Epic win. Thanks guys, this is a really neat technique! I was thinking the solution must be something like reduce but with two values, the due amount and the cards, but I couldn't figure out how to get the cards to "map". Turns out conj was the missing piece of the puzzle. Thanks again!
On Thu, May 2, 2013 at 5:34 PM, Gavin Grover <gavingroovygro...@gmail.com> wrote: > Is this code applying an amount due against a customer's list of credit > cards? If so, there seems to be a bug. The third line should be: > > card.appliedBalance = min(due, card.balance) > > and the Clojure code I'd write is: > > (defrecord Card [balance applied-balance]) > > (defn apply-due-to-cards [[due new-cards] card] > (let [applied-bal (min due (:balance card))] > [(- due applied-bal) > (conj new-cards (->Card (:balance card) applied-bal))])) > > (assert (= > (reduce apply-due-to-cards [100 []] > [(->Card 10 0) (->Card 30 0) (->Card 150 0)]) > [0 > [(->Card 10 10) (->Card 30 30) (->Card 150 60)]])) > > Also four lines long like the Ruby example, but it's easier to debug when > there's a bug just by changing `reduce` to `reductions`. It's also > threadsafe, and can be parallelized for large datasets by using the Clojure > 5 Reducers library. > > > On Friday, May 3, 2013 5:21:46 AM UTC+8, Steven Degutis wrote: >> >> Given pseudo-code (Ruby-ish): >> >> due = 100 >> cards = cards.map do |card| >> card.applied_balance = max(0, due - card.balance) >> due -= card.applied_balance >> >> Notice how due changes at each turn, and each successive item in >> "cards" sees the change. >> >> What's an idiomatic way to do this in Clojure without using refs? >> >> -Steven > > -- > -- > 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/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 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/groups/opt_out.
