Wilson MacGyver a écrit :
> More newbie questions. :)
>
> If I have two sequences as follow:
>
> (2 3 4 5 6 7 8 9 10)
> (4 6 8 10)
>
> what's the best way to subtract the 2nd sequence from the first one?
>
Is the order of the second sequence important? If not:
(defn subtract [a b]
(remove (into #{} b) a)) ; turns b into a set for efficient
(logarithmic) lookup
; user=> (subtract [2 3 4 5 6 7 8 9 10] [4 6 8 10])
; (2 3 5 7 9)
It works well as long as you don't have nil or false values in the
second seq (in such cases you'll have to use 'contains?).
Christophe
--
Professional: http://cgrand.net/ (fr)
On Clojure: http://clj-me.blogspot.com/ (en)
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