Flatten a Sequence

[Charlie Griefer]

At our initial meeting at the library (2 months ago), Brandon and I worked through 4Clojure problem #28, Flatten a Sequence (see http://www.4clojure.com/problem/28).

Brandon had sent an email with the code we came up with. https://gist.github.com/bitmage/37fa6e453dd4970d4c2d

It still needed (or needs) some refactoring, but overall it worked, and was a good learning experience.

I bring it up now because I just saw somebody post their solution to twitter. Check it out: https://www.refheap.com/86732

letfn and build are new to me. Need to dig into those in the docs.

Thought you folks might find it interesting.

--

Charlie Griefer

http://charlie.griefer.com

"Give light, and the darkness will disappear of itself." 

-- Desiderius Erasmus

[Paul M Bauer]

(fn f [x] (if (coll? x) (mapcat f x) [x]))

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[Charlie Griefer]

Wow that’s… concise :)

Will play around with that one later on.

[Andy C]

this is my - more classic  - version:

(fn X [y]
  (reduce concat
    (map (fn [x] (if(coll? x) (X x) [x])) y)
  )
)

now I now mapcat :-). Also it seems that some ppl factor out (if (coll? ...) ...) from reduce/mapcat - interesting

Cheers,
A.

[Brandon Mason]

Concise because mapcat does most of what you would want to do with flatten.  :-)

Does anyone know if mapcat is a clojure equivalent to what they call 'flatmap' in Scala?

Brandon Mason

Torchlight Software

623.882.4246

[Paul Bauer]

roughly, yes

[Andy C]

http://stackoverflow.com/questions/20363205/what-are-the-differences-between-mapcat-in-clojure-and-flatmap-in-scala-in-terms

[Torchlight]

1	"flatMap is the bind function in List monad" No, flatMap is the common Scala name for all bind functions. –  Alexey Romanov Dec 6 '13 at 4:25

That I suppose was the answer I was looking for.  So they are equivalent for purposes of collections.