Inserting element into sequence while mapping over it in Clojure

Question

I have a vector of the form [ ["H"] ["B"] ["ER"] ["W"] ] and I want a vector of the form [ ["H"] ["B"] ["E"] ["R"] ["W"] ] with the E and the R naturally separated.

I'm quite familiar with map (and reduce) and have been using them a lot but for some reason I can't think of a way to do this easily using map.

Can map produce two elements or more for each input it receives from a sequence? If so how?

glts · Accepted Answer · 2016-09-04 13:47:46Z

4

mapcat is what you’re looking for.

With mapcat you return a collection for each input element. The collections are concatenated into the result. For example:

(vec
  (mapcat #(map (comp vector str) (first %))
          [["H"] ["B"] ["ER"] ["W"]]))

answered Sep 4, 2016 at 13:47

glts

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1 Comment

Luke Fernandes Over a year ago

Thanks!! I knew there must have been an elegant solution I was missing.

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