I think you also need 

    let ( ~- ) x = if x <> min_int then -x else raise Overflow

(~- is unary minus, commonly typed in as "-")

You still get
    -1073741824=1073741824
being true if you type in the exact literals. I think fixing this
requires tweaking the parser.

-- Manos

On Mon, Jun 14, 2004 at 05:55:52PM +0200, Xavier Leroy wrote:
> Dear John,
> 
> > 2. Is there a way to tell OCaml that ints really are either 
> >    (a) bignums or
> >    (b) overflow-protected ints (as in SML/NJ, for instance)
> 
> Solution (b) is much easier, provided you don't care much for
> performance (probably true for an intro course).  Stick the following
> definitions in, say, CS101.ml
> 
>   exception Overflow
> 
>   let ( + ) a b =
>     let c = a + b in
>     if (a lxor b) lor (a lxor (lnot c)) < 0 then c else raise Overflow
> ...

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