Ocaml, why this code does not work?

Question

let rec prime : int -> bool
 = fun n -> let rec f a = if (a = 1) then 1 
                       else if (n mod a) = 0 then 0 
                       else if ((f a-1) = 1) then 1 
                       else 0 
                       in 
                       if ((f n-1) = 1) then true 
                       else false

As you can see from my code, I want to implement a function which can tell given number is prime or not.

I can compile and run this code, but for all X function tell "false".

Why this happens?

Thanks in advance. :)

I recommend to always add white spaces around binary operators. You get less confused by writing f n - 1 than f n-1 which many beginners misread as f (n-1). — camlspotter

Jeffrey Scofield Jeffrey Scofield · Accepted Answer · 2016-09-27T20:16:00

0

votes

The expression:

f n-1

is parsed like this:

(f n) - 1

You need to write this:

f (n - 1)

Ocaml, why this code does not work?

2 Answers