count not supported on this type

[Roelof Wobben]

I try to make this assigment :

Write the function (contains-duplicates? sequence) that takes a sequence as a parameter and returns true if sequence contains some element multiple times. Otherwise it returns false.

So I did this :

(defn contains-duplicates? [a-seq]
  (let [element (fn element [a-seq] (count a-seq) )]
     (= (map element a-seq)1)))

But then I see this message : UnsupportedOperationException count not supported on this type: Long  clojure.lang.RT.countFrom (RT.java:556)

When I change map to apply I see this message : ArityException Wrong number of args (5) passed to: structured-data$contains-duplicates-QMARK-$element  clojure.lang.AFn.throwArity (AFn.java:437)

Where did I misunderstood this page : http://iloveponies.github.io/120-hour-epic-sax-marathon/structured-data.html

Roelof

[James Reeves]

Your function is essentially:

    (= (map count coll) 1)

So you're applying the function "count" to each element in the collection. Let's say your collection is:

    [1 2 3]

Then you're trying to evaluate:

    [(count 1) (count 2) (count 3)]

Clojure is raising an exception that says "I can't count a number, I can only count collections".

- James

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[Roelof Wobben]

oke,

Then I have to fnd another way to see how many times a number is present in a collection.

I thought count  could do that.

Roelof

Op vrijdag 9 mei 2014 20:24:29 UTC+2 schreef James Reeves: