Re: [Caml-list] Clarification for the configuration of comparison functions

[Ben Millwood <bmillwood@janestreet.com>]

On 10 September 2014 13:51, Gerd Stolpmann <info@gerd-stolpmann.de> wrote:
> Am Mittwoch, den 10.09.2014, 13:41 +0100 schrieb Pippijn van Steenhoven:
>> Also, if you store the hash before the actual value, compare will
>> probably stop comparing after it finds that the hashes are not equal, so
>> you can simply use the polymorphic compare on t_cmp. I don't know this
>> for sure, since I haven't looked at the source, but I would assume this
>> is true.
>
> The OCaml manual doesn't define compare for tuples, so you cannot
> exploit that. I wouldn't bet that compare runs from left to right over
> the values, as OCaml is known for sometimes preferring right to left.
> But maybe this could be a future language feature? If the OCaml manual
> defined compare on tuples, this would in deed be a fine trick.

On the other hand, perhaps the fact that no-one is sure without
checking whether or not this works is indication enough that it is too
clever a trick for its own good, and just doing the obviously-right
thing is a more sensible option :)