Re: [Caml-list] Physical counterpart to Pervasives.compare?

[Edgar Friendly <thelema314@gmail.com>]

Edgar Friendly wrote:
> Elnatan Reisner wrote:
>> I'm afraid of getting into trouble with Obj.magic, but what would this do:
>> let f (x:'a) (y:'a) = compare (Obj.magic x) (Obj.magic y)
>> ? Or would annotations make any difference:
>> let f (x:'a) (y:'a) = compare (Obj.magic x : int) (Obj.magic y : int)
>>
>> -Elnatan
> 
> Nope, Obj.magic and casting only have compile-time effects, the code
> given compiles exactly the same as [let f x y = compare x y].
>
It looks like I'm wrong on this - there's versions of compare
specialized for floats, strings and ints.  Maybe you *could* trigger the
use of the caml_int_compare by this kind of type system manipulation.
It looks quite safe to use on non-ints.

Testing on your platform is possible, by trying to find store pointers
to ints, so that caml_compare compares the ints, but the tricked
caml_int_compare compares the pointers, and gets a different result.

E