[Caml-list] coercing to a #-type

[Caml-list] coercing to a #-type

[Henri Dubois-Ferriere]

can coercing an object to a #-type ever change the type of the object?

[i tried to come up with some instance where this would happen, but could 
not, and on thinking about it i would guess that since a #-type is 'open', 
it makes no sense to coerce to such a type.]


A somewhat related question:

class a = object method bla = 1 end
are the types 

#a

and 

< bla : int; ..> 

equivalent? (in the sense that using on instead of the other will 
always give identical results)


Thanks
Henri

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Re: [Caml-list] coercing to a #-type

[Jacques Garrigue]

From: Henri Dubois-Ferriere <henridf@lcavsun1.epfl.ch>

> can coercing an object to a #-type ever change the type of the object?
> 
> [i tried to come up with some instance where this would happen, but could 
> not, and on thinking about it i would guess that since a #-type is 'open', 
> it makes no sense to coerce to such a type.]

What do you mean by "coercing"?
If you mean (o :> #a), then indeed it is pointless, as it is just
equivalent to (o : #a) (no subtyping is introduced).

> A somewhat related question:
> 
> class a = object method bla = 1 end
> are the types 
> 
> #a
> 
> and 
> 
> < bla : int; ..> 
> 
> equivalent? (in the sense that using on instead of the other will 
> always give identical results)

Indeed they are equivalent. #a is just a convenience to make printed
types more readable.

      Jacques Garrigue

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