Convert clojure persistant vector to maps

Question

I'm trying to learn clojure.

I am calling a function which is returning me an array of strings..

If I do:

(let [items (get-all-items)]
    (println (type items))
    (items))

the type of items is shown as class clojure.lang.PersistentVector where as the items value is like so:

[["Dogs"] ["Cats"] ["Capybaras"] ["Pygmy Hedgehogs"]]

I would like to convert this to a map in a format like this:

{ "Dogs" "Cats" "Capybaras" "Pygmy Hedgehogs" }

Does that make sense? Clojure maps can contain list of strings right?

I am only doing this because if I have it as a map, I can check if I have a pet in the list like this:

(contains? pets "Dogs")
; assuming the map is stored in pets variable

that fails if pets is a vector.

So If I can convert that to maps, how do I convert it? if not, how do I search for something in the vector?

(I like working with maps so I'd rather have maps - unless there is a strong reason not to do so)

_{ps: I've tried converting with into but that doesn't work either.}

It sounds like you want a set, not a map. Does "Dogs" have a value other than itself, or are you just testing for membership? — Francis Avila
@FrancisAvila, just testing for membership.. so maps always have a value with them? then sets would be better! — Alexander

Francis Avila Francis Avila · Accepted Answer · 2013-04-17T16:17:22

I suspect what you really want is a set, not a map. Maps store a value associated with a specific key. Sets store a unique list of values.

If your only use case is testing for membership, then you definitely want a set. You want a map if you are also associating some data with that key.

It's very easy to produce a set from any sequence. In your case:

(set (flatten items))
;;=> #{"Pygmy Hedgehogs" "Dogs" "Cats" "Capybaras"}

flatten removes the nesting on your lists giving you a sequence of strings. set consumes the sequence and returns a set of the unique values in that sequence.

Convert clojure persistant vector to maps

2 Answers