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Date: Fri, 11 Oct 2002 08:42:21 +0200
From: Florian Hars <florian@hars.de>
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To: "Scott J," <jscott@planetinternet.be>
CC: caml-list@inria.fr
Subject: Re: [Caml-list] Runtime overflow and what to do
References: <00bd01c2706d$e7cd68e0$0100a8c0@janxp>
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Scott J, wrote:
> Because an integer number is represented by a fixed number of bytes I 
> will get a runtime overflow if n is chosen too large.

You have to check explicitly:

# exception Overflow;;
exception Overflow
# let fact n =
    let rec fact_r acc n =
     if n = 1 then acc
     else if max_int / acc > (n-1) then fact_r (acc * n) (n - 1)
     else raise Overflow
    in
    fact_r 1 n;;
val fact : int -> int = <fun>
# fact 12;;
- : int = 479001600
# fact 13;;
Exception: Overflow.

Yours, Florian

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