CODEWITHSUNDEEP
clojure
shekhar
shekhar

Reputation: 49

Getting Execution error (StackOverflowError) when evaluating a function on larger range of values

I'm learning Clojure and solving exercises from SICP book in the process. I get this error when evaluating (search-for-primes 1001 10000) but when called on smaller values (search-for-primes 101 1000) it works fine.

This seems to be a memory issue but I'm unable to zero in on the cause of it. Would love your help. Thank you. Below is the code.

(defn square [x]
  (* x x))

(defn divides? [a b]
  (= (rem b a) 0))

(defn find-divisor [n test-divisor]
  (cond
    (> (square test-divisor) n) n
    (divides? test-divisor n) test-divisor
    :else (find-divisor n (+ test-divisor 1))))

(defn smallest-divisor [n]
  (find-divisor n 2))

;;return true if prime
(defn prime? 
  [n]
  (= n (smallest-divisor n)))

;;return the first of the three consecutive prime numbers
(defn search-for-primes [low high]
  (if (< low high) 
    (cond 
      (and (prime? low) (prime? (+ low 2)) (prime? (+ low 4))) low 
      :else (search-for-primes (+ low 2) high))))

Upvotes: 0

Views: 418

Answers (1)

corvuscorax
corvuscorax

Reputation: 5940

You don't show the actual error you're getting, but I'll guess that it has something to do with the stack overflowing.

Unlike Scheme, Clojure does not support tail call elimination, so you probably need to look at loop/recur, see https://clojuredocs.org/clojure.core/loop for example.

Upvotes: 6

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