clojure - What is causing this NullPointerException? -

i'm using project euler questions me learn clojure, , i've run exception can't figure out. nillify , change-all defined @ bottom reference.

(loop [the-vector (vec (range 100))        queue      (list 2 3 5 7)]     (if queue         (recur (nillify the-vector (first queue)) (next queue))         the-vector)) 

this throws nullpointerexception, , can't figure out why. part of code can see could throw such exception call nillify, doesn't seem queue ever gets down 1 element before exception thrown---and if queue become empty, that's if statement for.

any ideas?

"given vector, value, , list of indices, return vector w/everthing @ indice=value"

(defn change-all [the-vector indices val]     (apply assoc the-vector (interleave indices (repeat (count indices) val)))) 

"given vector , val, return vector in entries indices equal multiples of val nilled, leave original untouched"

(defn nillify [coll val]     (change-all coll (range (* 2 val) (inc (last coll)) val) nil)) 

the problem sexpr is

(inc (last coll)) 

you're changing contents of vector, can't use determine length anymore. instead:

(count coll) 

as matter of style, use let bindings:

(defn change-all [the-vector indices val]   (let [c (count indices)         s (interleave indices (repeat c val))]     (apply assoc the-vector s)))  (defn nillify [coll val]   (let [c (count coll)         r (range (* 2 val) c val)]     (change-all coll r nil)))  (loop [the-vector (vec (range 100))        [f & r]    '(2 3 5 7)]   (if r      (recur (nillify the-vector f) r)      the-vector))