Dear Clojure Group,
I am currently reading the online book Pro
Git<https://docs.google.com/document/d/1pms_fnr0m2xlYH_4CB3pMeWBdIBlly4CQGMWuogOntg/edit?hl=en>.
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 still a beginner, but I am afraid I won’t be
able to figure out immediately what this code is doing a few weeks from now.
However, I am sure there must be a better way of translating the Ruby
version into Clojure. 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
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