Add items in a list/sequence in Clojure

Question

There has to be a simple way to do this, and I am obviously missing it :|

How do you add the items in a list\sequence (not clear on the difference) in clojure?

I've tried the following:

Clojure> (add [1 2 3])
java.lang.RuntimeException: Unable to resolve symbol: add in this context
Clojure> (+ [1 2 3])
java.lang.ClassCastException: Cannot cast clojure.lang.PersistentVector to java.lang.Number
Clojure> (apply merge-with + [1 2 3])
java.lang.IllegalArgumentException: Don't know how to create ISeq from: java.lang.Long
Clojure> (add-items [1 2 3])
java.lang.RuntimeException: Unable to resolve symbol: add-items in this context

Yes, @NathanHughes - that is what I was looking for. I don't know why I couldn't figure something so simple out, but yes - that was it. — javamonkey79
– javamonkey79, Commented Dec 2, 2011 at 21:28

Community · Accepted Answer · 2017-05-23 11:59:30Z

9

(+ 1 2 3)

...will do it. @Nathan Hughes's solution:

(apply + [1 2 3])

...works if you have a reference to the sequence rather than defining it inline, e.g.:

(def s [1 2 3])
; (+ s) CastClassException
(apply + s) ; 6

As @4e6 notes, reduce also works:

(reduce + s) ; 6

Which is better? Opinions vary.

edited May 23, 2017 at 11:59

CommunityBot

11 silver badge

answered Dec 2, 2011 at 20:01

Craig Stuntz

127k12 gold badges257 silver badges275 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

4e6 Over a year ago

I believe (reduce + [1 2 3]) is more idiomatic.

Craig Stuntz Over a year ago

@4e6: You may be right.

Michiel Borkent Over a year ago

(reduce + [1 2 3]) doesn't really make sense to me, since + already uses reduce: github.com/richhickey/clojure/blob/…

Adrian Mouat Over a year ago

@4e6 as far as I can tell, a lot of clojurians seem to prefer (apply + [1 2 3]), although other lisps prefer reduce. I guess "apply" conveys the intent of the function better.

mikera Over a year ago

(reduce + [1 2 3]) is probably best once the new Reducers functionality is released - reduce will get a lot more optimisations: clojure.com/blog/2012/05/08/…

Collectives™ on Stack Overflow

Add items in a list/sequence in Clojure

1 Answer 1

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related