CODEWITHSUNDEEP
clojure
georgek
georgek

Reputation: 877

how to find the position of last occurrence of element in sequence with Clojure?

I want to find the position of the last occurence of an element in a sequence. Testing some solutions I came up with, 

user> (def numbers (repeatedly 100 #(rand-int 100)))
#'user/numbers

user> (time ((zipmap numbers (range)) 22))
"Elapsed time: 0.865193 msecs"
90

user> (time (last (keep-indexed #(if (= 22 %2) %1) numbers)))
"Elapsed time: 1.600483 msecs"
90

Is there a more concise built-in that does this?

Upvotes: 3

Views: 886

Answers (1)

ponzao
ponzao

Reputation: 20944

You could use lastIndexOf after you cast the object to the correct type:

(.lastIndexOf numbers (int 22))

The method is documented here: http://docs.oracle.com/javase/6/docs/api/java/util/List.html#lastIndexOf(java.lang.Object)

Upvotes: 1

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