Solving a 4Clojure problem, I got this answer to compress a sequence (problem 30):

#(map first (partition-by identity %))

What would be the best approach to have this work with plain numbers too?

My solution was this:

(defmulti comp class)
(defmethod comp java.lang.Long [x] x)
(defmethod comp :default [x] (map first (partition-by identity %)))

The code is more than tripled. Are there better solutions? Shorter? More idiomatic? I tried extending java.lang.Long with ISeqable, but failed miserably.


Nice solution. Your solution already works great with sequences of numbers (and more) already. The comp multi-method is not a good idea. It is a function which can take either a seq or a number. You should avoid creating functions that take arguments that can be different types (it is confusing and suggests your might be better off with 2 functions or a protocol) unless there is a really good reason. In this case comp does not add anything useful (why did you add it? do you have an example use case?)

  • \$\begingroup\$ Hey, thanks! There's no real reason, I was just messing a little to learn things :) I agree it doesn't make much sense like this, but I just wanted to try what possible solutions to similar scenarios would be. \$\endgroup\$ – Dario Oddenino Nov 3 '15 at 22:51
  • \$\begingroup\$ Gotcha. If you really want to just check the type of something, also consider just using a test: (if (number? x) x blah) instead of using dispatch. \$\endgroup\$ – Timothy Pratley Nov 3 '15 at 23:16

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