CODEWITHSUNDEEP
functional-programmingschemelispracketinfinite-loop
MitakaJ9
MitakaJ9

Reputation: 301

Scheme (Racket) Properly written function not working with some inputs

So I have written I function in racket that calculates Sums:

(define (sum term a next b)
  (if (> a b)
      0
      (+ (term a) (sum term (next a) next b))))

Term is what function is applied to every argument. A is the beginning next is how we advance to the next element (i.e. a2 = 2*a1 or a2 = a1 +1 etc.) and b is the final element.

There are 2 additional functions:

(define (square x) (* x x))
(define (inc x) (+ x 1))

If I type:

(sum square 1 inc 5) I get which is correct 55

But if I type:

(sum square 1 square 5)

I am stuck in a loop!? Why is that a2 should be a1*a1 and a3=a2*a2 and a should surpass b so the condition to end the recursion would be fultifield. Very strange.

Upvotes: 1

Views: 165

Answers (1)

Diego
Diego

Reputation: 1819

Your sum function will loop forever because (square 1) always evaluates to 1 and will never be greater than 5.

Upvotes: 8

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