Re: Persistence of limited tagged types

[Jano <nono@celes.unizar.es>]

Robert Spooner dice...
> 
> Stephen Leake wrote:
> > Robert Spooner <rls19@psu.edu> writes:
> > 
> > 
> >>I think that if you use 'output to put the object onto the disk, it
> >>will put the external representation of the tag out with it. Then if
> >>you use 'imput to read it back in as an object of type Object'class
> >>you will get what you're looking for.
> > 
> > 
> > That is certainly true. The trick is to get an object of type
> > Object'class; it's an unconstrained type, so you can't just do:
> > 
> > An_Object : Object'class;
> > 
> > In practice, you need to know the concrete object type _before_ you
> > call 'input, so you can allocate (or declare) an object of that type.
> > That means some representation of the tag must be stored in the
> > external file separately from the object, so you can read it first.
> > 
> 
> The input attribute is a function, so you can initialize an object of 
> the class using it without a priori knowledge of the type.

Yes, the whole matter arises because we are discussing limited types 
that can't be created that way.

-- 
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Jano
402450.at.cepsz.unizar.es
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