`get` looks up a key or index without throwing merely because it is absent or the collection is unsupported. Its forms are `(get coll key)` and `(get coll key not-found)`: an unsuccessful lookup returns `nil` by default, or the supplied `not-found` value. The function is primarily for maps, but its result depends on the collection type. section 8.2.2 section 8.2
Map lookup and a fallback
`(get {:a "a" :b "b"} :a)` returns `"a"`. `(get {:a "a"} :missing "Not found")` returns `"Not found"`. A fallback also handles an unsupported collection: `(get (list 1 2 3) 1 "Not found")` returns `"Not found"`. section 8.2.2
The same call has different meanings across supported inputs:
- For maps, including records and `java.util.Map` implementations, it retrieves the value associated with a key. For a set, it returns the matching element. section 8.2.2
- For a vector, string, or native Java array, a numeric key selects an indexed item. `nil` can be passed as the collection; it yields `nil` or the supplied fallback. section 8.2.2
- A fallback does not prevent every exception: an incompatible key type can cause `ClassCastException` with a sorted map or sorted set. Very large numeric indices can be truncated when used with vectors, strings, or arrays. section 8.2.2
(def mixed-bag [{1 "a"} [0 2 4] nil "abba" 3 '(())])
(map #(get % 1) mixed-bag) ; #1
;; ("a" 2 nil \b nil nil)
A single lookup over a mixed collection yields a map value, vector item, string character, or `nil`, depending on each input. section 8.2.2
Choose the access operation by the result you need. `find` returns a map entry rather than just its value; `get-in` follows a path through nested collections. Maps and keywords can also be called for map lookup. Use `get` when a value—or a chosen fallback—is the useful result. section 8.2.2
