Int64 comparison

Int64 comparison

[Elnatan Reisner]

Do the polymorphic ordering functions -- (<), (>), etc. -- correspond  
to the numerical ordering for Int64s and Int32s? I assume so, but I  
didn't see this specified anywhere.

If the answer is 'yes', is there a reason I should prefer
Int64.compare n1 n2 < 0
to
n1 < n2
? If there's no specific reason the first is better (and I don't see  
why it would be), I definitely prefer the second.
-Elnatan

Re: [Caml-list] Int64 comparison

[Till Varoquaux]

Taken from Int64.ml:

let compare (x: t) (y: t) = Pervasives.compare x y

compare seems to be there for functor applications (e.g. Set.Make
needs it). I would use standard comparison; it should be exactly the
same except it will be more legible and might be a tad faster.

Till


On Tue, Mar 17, 2009 at 8:51 AM, Elnatan Reisner <elnatan@cs.umd.edu> wrote:
> Do the polymorphic ordering functions -- (<), (>), etc. -- correspond to the
> numerical ordering for Int64s and Int32s? I assume so, but I didn't see this
> specified anywhere.
>
> If the answer is 'yes', is there a reason I should prefer
> Int64.compare n1 n2 < 0
> to
> n1 < n2
> ? If there's no specific reason the first is better (and I don't see why it
> would be), I definitely prefer the second.
> -Elnatan
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

Re: [Caml-list] Int64 comparison

[Jérémie Dimino]

Le mardi 17 mars 2009 à 08:51 -0400, Elnatan Reisner a écrit :
> Do the polymorphic ordering functions -- (<), (>), etc. -- correspond  
> to the numerical ordering for Int64s and Int32s? I assume so, but I  
> didn't see this specified anywhere.

Yes, int64s and int32s are represented in memory by custom blocks [1],
so there is a specific comparison functions for them.

> If the answer is 'yes', is there a reason I should prefer
> Int64.compare n1 n2 < 0
> to
> n1 < n2
> ?

They may be compiled differently if the compiler does not know that n1
and n2 are of type int32 or int64 in the second case, but the result
will be the same. You can have look at [2], paragraph "Polymorphic
types" for details.

Jérémie

[1] http://caml.inria.fr/pub/docs/manual-ocaml/manual032.html#toc136

[2] http://www.ocaml-tutorial.org/performance_and_profiling