'for' can be handy when unpacking compound lines: (ns foobar (:require [clojure.java.io :as io]))
(defn parse-acl [acl-file] (with-open [r (io/reader acl-file)] (apply merge-with into (for [[status users path] (map #(.split % "\\|") (line-seq r)) :when (= "avail" status) user (.split users ",")] {user [path]})))) Justin On Mar 3, 9:15 pm, Stefan Rohlfing <stefan.rohlf...@gmail.com> wrote: > Dear Clojure Group, > > I am currently reading the online book Pro Git <http://progit.org/book/>. In > chapter 7.4 <http://progit.org/book/ch7-4.html> (section “Enforcing a > User-Based ACL System”) there is a task of reading in an access control list > (ACL) file, such as the following > > # avail/unavail | users | path > avail|nickh,pjhyett,defunkt,tpw > avail|usinclair,cdickens,ebronte|doc > avail|schacon|lib > avail|schacon|tests > > and printing out a map of the form { "user1" [path 1, path 2], "user2" > [path2, path3] ...}. > > The author of the book provides a solution in Ruby, which I find relatively > easy to follow, despite not having written any Ruby code before: > > def get_acl_access_data(acl_file) > # read in ACL data > acl_file = File.read(acl_file).split("\n").reject { |line| line == '' } > access = {} > acl_file.each do |line| > avail, users, path = line.split('|') > next unless avail == 'avail' > users.split(',').each do |user| > access[user] ||= [] > access[user] << path > end > end > access > end > > I then tried the same in Clojure, but found my solution to be much less > readable compared to the Ruby code: > > (use '[clojure.string :only (split)]) > > (defn get-acl-access-data [file] > (let [acl (split (slurp file) #"\n")] > (apply merge-with #(into %1 %2) > (map (fn [[avail users path]] > (let [users (split users #",")] > (reduce (fn [acc user] > (when (= avail "avail") > (assoc acc user [path]))) > {} users))) > (map #(split % #"\|") acl))))) > > ;; Output: > ;; {"schacon" ["lib" "tests"], > ;; "usinclair" ["doc"], > ;; "cdickens" ["doc"], > ;; "ebronte" ["doc"], > ;; "tpw" [nil], > ;; "defunkt" [nil], > ;; "pjhyett" [nil], > ;; "nickh" [nil]} > > Maybe it is just because I am an ambitious beginner at best, but I am afraid > I won’t be able to figure out immediately what this code is doing in a few > weeks. > > However, there probably is a better way of translating the Ruby version into > Clojure. With "better" I mean easier to follow. My main goal is on clarity, > as I often struggle organizing my code in a way I would consider readable. > > I therefore would be glad for any ideas of improvement. Any suggestions are > highly welcome! > > Best regards, > > Stefan -- 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