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Subject: [Caml-list] A (much less) frustrated beginner
From: Tyler Eaves <tyler@ml1.net>
To: caml-list@inria.fr
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I think I'm beginning to get it. Attached find my second try at a prime
number generator.

This one is distinguished from my first by two important differences:

1: It is written (I think) in a completly functional style 
2: It actually *works*. It's pretty fast too. Running as an optimized
binary on my system (Athlon @ 950mhz under FreeBSD 5.1) it can calculate
the first 15104 primes (Highest is 165161) with one minute of CPU time.

Thanks again for all your help!

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(*  primes2.ml 
    Prime number generator, take 2
    Tyler Eaves <tyler@ml1.net>
    *)
   
exception Not_prime;;
exception Its_Prime;;

let rec isprime n primes = (
    try
        List.iter (fun x -> if n mod x = 0 then raise Not_prime else if sqrt
        (float_of_int n) < (float_of_int x) then raise Its_Prime else ()) primes;
        Printf.printf "%d is PRIME!\n" n; 
        isprime (n+2) (List.concat [primes; [n]])
    with 
        Not_prime -> isprime (n+2) primes
        | Its_Prime -> (Printf.printf "%d is PRIME!\n" n; 
          isprime (n+2) (List.concat [primes; [n]]))
    );;

isprime 3 [2];;
    

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