* yoann padioleau:

>>> Are you sure ? I thought it was just a function to get rid temporary
>>> of the typing system, a kind of cast operator.
>>>
>>
>> It is, but how would you define such a operator?
>
> obj.ml contains:
>   external magic: 'a -> 'b = "%identity"
>
> So I guess there is no bit-wise copy involved.

Ahem, "%identity" means just that, I think.