Linear search examines collection elements sequentially until a match is found or the collection is exhausted. In Clojure, use explicit scanning functions rather than treating contains? on vectors as an element search. section 8.2.3
Scanning a sequential collection
(some #{:a} [:a :b :c]) ;; :a (some #(= nil %) [:a nil :c]) ;; true some accepts a predicate and returns the matching truthy result; an equality predicate allows searching for nil. section 8.2.3
Choose the operation according to the collection and the question being asked:
- Do not use (contains? [1 2 3 4] 4) to find an element; on vectors, contains? checks whether an index exists, so this returns false. section 8.2.3
- Use .contains for supported Java collection types or strings when direct inclusion or substring searching is the intended operation. section 8.2.3
(.contains [:a :b :c :d] :a) ; #1
;; true
(.contains {:a 1} :a) ; #2
;; IllegalArgumentException No matching method found
(.contains "somelongstring" "long") ; #3
;; true
Compare direct inclusion on a vector and substring searching on a string with the unsupported map case. section 8.2.3
