Contains map in a list of maps

Question

I have a list of maps and I need to know if one other map contains in this list:

List of maps: [{:a 1} {:a 2} {:a 3}]

My map: {:a 2}

Expected output: true

I had tried to use contains but do not work. I come up with a solution but I don't think its a good one:

(map 
   (fn [x] 
      (if (= x {:a 1}) 
         true 
         false))
   [{:a 1} {:a 2} {:a 3}])

The result of this code I'm getting a list of true or false, and I will need to see if contains one true in this list.

So my question is, exist some way easier to verify if exist a map in a list of maps?

score 2 · Accepted Answer · answered May 23 '19 at 23:16

I think this question can be generalized to "how can I tell if a sequence contains a value?" some is good for this:

(some pred coll)

It returns the first logical true value from pred by invoking it with each item of coll.

For example, the predicate can be a simple equality check:

user=> (some #(= % {:foo 1})
             [{:foo 1} {:foo 2}])
true

It's also common to use sets as predicates:

One common idiom is to use a set as pred, for example this will return :fred if :fred is in the sequence, otherwise nil: (some #{:fred} coll)

1 Answers1