What's expecting a function in this clojure code?

Question

going through the exercises in the fp-oo book and i'm having trouble with an early exercise to add squares. Here's my code:

 (defn square [n]
   (* n n))

 (defn add-squares [l]
   (cond
     (nil? l) 0
     :else (+ (square (first (l))) (add-squares (rest (l))))))

This example:

(add-squares '(2 2 2 2))

should return

but fails with this exception:

ClassCastException clojure.lang.PersistentList cannot be cast to clojure.lang.IFn  user/add-squares (NO_SOURCE_FILE:4)

which i guess means i'm trying to pass a function somewhere instead of a list which was expected. Can someone tell me which part of the code is the culprit?

Thanks, James

Chiron · Accepted Answer · 2014-01-21 13:44:43Z

4

This is wrong:

(first (l))

This means that you are calling l as a function.

You should use:

(first l)

And of course, the same thing for (rest (l))

edited Jan 21, 2014 at 13:44

answered Jan 21, 2014 at 13:38

Chiron

20.3k18 gold badges84 silver badges135 bronze badges

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

1 Comment

james lewis Over a year ago

thanks, removing those parentheses around the l in the call to first and rest did it.

Collectives™ on Stack Overflow

What's expecting a function in this clojure code?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related