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Same label in different types, how do people solve this?
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Date: -- (:)
From: Pierre Weis <weis@p...>
Subject: Re: Same label in different types, how do people solve this?
> Mattias Waldau wrote : 
> > In Ocaml, you cannot have the same label in different types, see the
> example
> > below where point_2d hides point_3d.
> 
> Troublemaker :-). There is a thread on this topic on comp.lang.functional. 
> Please, FAQ maintainer, this is very definitely FAQ material!

Feel free to propose an entry for the FAQ (in english and french
please): I would be glad to add it.

[...]
> Pierre Weis wrote
> > I would suggest another syntactic notation to specify the type to
> > which a label belongs: label@@type.
> > 
> > {x@@p2d = 0; y = 5}
> > r.x@@p2d
> 
> I don't want to start a syntax war, but I think Ocaml is already suffering
> a bit from too much added syntax and this doesn't look good to me. Jacques' 
> reuse of ":" (I know, it applies to the whole record and not a label) is 
> easier on my eyes, which already associate ":" with typing. 
> 
> -- Brian

The notation I suggested is simpler to implement and specify: there is
nothing new in type constraints propagation and label overloaing
resolution strategy: just a notation to specify the type to which a
label or constructor belongs to in the same spirit as usual
qualification of names in the module system.

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://cristal.inria.fr/~weis/