posted an update

I was proud of myself for coming up with a terse solution to @4clojure Problem 33 "Replicate a Sequence" until I discovered "interleave" doesn't accept 1 argument in older versions of clojure

So for Clojure 1.6.0, my solution:

#(apply interleave (repeat %2 %1))

will satisfy the following when replacing the fill-in-the-blank symbol:

(= (__ [1 2 3] 2) '(1 1 2 2 3 3))

(= (__ [4 5 6] 1) '(4 5 6))

Unfortunately, on 4clojure, the second example above fails with an arity exception on interleave, i.e., wrong number of arguments. Then I came across this thread citing the same issue. So 4clojure must be using an older version of Clojure to verify the results... at least I wasn't going crazy!

Rather than re-implement interleave, my uninteresting workaround is to return the collection if n is 1:

#(if (> %2 1) (apply interleave (repeat %2 %1)) %1)

User _pcl came up with a great solution. Rather than repeating the sequences then combining them with interleave, the approach is to map the sequence onto a result that repeats each item and flatten the result. The "map then flatten" is expressed as mapcat in Clojure

So a better solution:

#(mapcat (partial repeat %2) %1)

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