I haven't looked at how the compare happens for polyvariants, but I assume
it's going to treat them as integers. And the integer value of the
polymorphic variants is a simple hashing-type function (byterun/hash.c:
caml_hash_variant). A multiplication by 223 is involved for each character
of the variant name, so with a long enough name, compared to the integer
size, you'll get wraparound. The short names you have there are okay.

I'd be uncomfortable relying on this ordering, but I can imagine it would
make some things a lot simpler...



On Wed, Sep 4, 2013 at 6:17 PM, Daniel Bünzli
<daniel.buenzli@erratique.ch>wrote:

> Hello,
>
> I have this type
>
>   type weight = [ `W100 | `W200 | `W300 | `W400 | `W500 | `W600 | `W700 |
> `W800 | `W900 ]
>
> In the current compiler it has the property that `Wx00 < `Wy00 if x < y.
>
> The question is, is the order between polymorphic variants an invariant
> provided by the compiler or is it subject to change ?
>
> Best,
>
> Daniel
>
>
>
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