In Clojure, how to cons or conj the elements of a collection but not the collection itself?

cons currently behaves like so:

(cons '(1 2) '(3))
;=> ((1 2) 3)

I would like to achieve:

(magic-cons '(1 2) '(3))
;=> (1 2 3)

I couldn't find a resource for this yet this seems so simple I feel there sho开发者_运维问答uld be a built in function.

Or I just don't know the write words to describe this situation. Either way, please let me know. Thanks!

Edit: Please don't answer with "flatten" :P ie

(flatten (cons '(1 2) '(3)))

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You have to use concat:

clojure.core/concat
([] [x] [x y] [x y & zs])
  Returns a lazy seq representing the concatenation of the elements in the supplied colls.

Sample use:

user> (concat '(1 2) '(3))
(1 2 3)

---

I do believe you are looking for concat (think "concatenate lists"):

[Concat] returns a lazy seq representing the concatenation of the elements in the supplied colls.

In this case the usage would be:

(concat '(1 2) '(3))    

Note that unlike (many) other LISP-dialects, Clojure's concat yields a lazy sequence. See How to covert a lazy sequence to a non-lazy in Clojure? for how to "force" a sequence (this may or may not be useful/needed, depending upon larger context, but is important to keep in mind).

Happy coding.

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An alternative is "into".

into always returns the type of the first argument, unlike concat which always returns a list.

=> (into [2 4] '(1 2 3))
[2 4 1 2 3]

(into '(2 4) '(1 2 3))
(3 2 1 2 4)