Challenge - Count vowels

Count vowels

Find all the vowels in a string and count them.

Solution in Clojure language:


(defn vowels
  "Find and count all the vowels"
  [text]
  (cons text
        ((juxt identity count)
         (filter (set "aeiouAEIOU") text))))

(do
  (println (vowels "hello world"))
  (println (vowels "SoloLearn"))
  (println (vowels "Wake me up when it's all over"))
  (println (vowels "All for One, One for All")))

A few interesting notes about this Clojure implementation:

With the set function we convert the string of vowels to a set of characters.
The set can act as a predicate function in filter. It returns true, if the character examined exists in the set.
juxt is a curious function, short for juxtaposition. It combines several functions, applies each of them individually to the argument that follows, and creates a vector from the results.
So one of the functions applied is identity, that returns the argument itself, in this case the filtered letters. The other function is count that shows how many elements are in the collection.
Finally, cons adds the original text to the beginning of this vector, converting it to a lazy sequence.

[clj] count vowels