Stackoverflow with recursive function

Question

let rec f a p n = if p n then a else a + f a p ( n - 1 )
let a, p, n = 3, ( fun x -> x = 1 ), 4
f a p n

Getting stackoverflow when n <= 0. Not sure how to get around this.

Trying to build rep here. Why the down vote?

Iter
– Iter

2013-04-26 18:18:15 +00:00
Commented Apr 26, 2013 at 18:18 — Iter
– Iter, Commented Apr 26, 2013 at 18:18

N_A · Accepted Answer · 2013-04-26 18:15:53Z

4

Your p = fun x -> x = 1 which, of course, checks if x is 1.

Your recursive call uses p on n, otherwise decrements n.

This will cause n to become more and more negative, resulting in infinite recursion since n will never be 1. To solve this you need to not call p with a value of n less than 1 or change your check function to do something other than check for a value of 1.

Maybe try let a, p, n = 3, ( fun x -> x <= 1 ), 4.

answered Apr 26, 2013 at 18:15

N_A

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1 Comment

ildjarn Over a year ago

It's also worth noting that if f were made tail-recursive then the code would "work" (i.e. not crash) with p as-is, as n would eventually underflow and count down from Int32.Max to 1.

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