420 PurelyFunctional.tv Newsletter

00 Unique elements.md

Unique elements

There's a function in Clojure called distinct that removes duplicates from a sequence. Your task is to write a function called uniques that removes elements that appear twice.

Examples

(uniques []) ;=> ()
(uniques [1 2 3]) ;=> (1 2 3)
(uniques [1 1 2 3]) ;=> (2 3)
(uniques [1 2 3 1 2 3]) ;=> ()
(uniques [1 2 3 2]) ;=> (1 3)

Thanks to this site for the challenge idea where it is considered Medium in Python. The problem has been modified from the original.

Please submit your solutions as comments on this gist.

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@fahadbuddy #{1} is a set.
(your-set key) means getting a value from the set, i.e. key or nil if it is not in the set.

E.g.

(map #{1} [1 2 3]) ; => (1 nil nil)

@farhadbuddy Note the use of “comp”. The set #{1} gets applied not to freqs but rather to the result of applying freqs to an element of xs.