Re: Runtime object type determination/ runtime generic instantiation

[Anthony Jenkins <abjenkins@mindspring.com>]

Jon S Anthony wrote:
> 
> Anthony Jenkins <abjenkins@mindspring.com> writes:
> 
> > The package I have to create is one for (un)directed graphs, where the
> > vertices can represent numbers, characters or strings (I'm thinking more
> > generically than these 3 types so I can possibly use it later) where the
> > node value type is given in a file.  Am I looking at this wrong?  I'm
> 
> It _seems_ like you certainly are looking at it "wrong".  Since you
> are already dealing with a higher level structure (the nodes), why
> don't you create a hierarchy of these?  Which would also be
> incrementally extensible, dynamically dispatchable, etc.  Here's a
> basic hack:
> 
>     type Node_Type is abstract tagged private;
>         -- or better yet, limited private
> 
>     -- all the basic operations.  Could be abstract as well or a mix.
> 
> ...
> 
>     type Number_Node_Type is abstract new Node_Type;
> 
>     ... all the common number operations...
> ...
>     type Real_Number_Node_Type is new Number_Node_Type with private;
> ...
>     type Integer_Number_Node_Type is new Number_Node_Type with private;
> 
>     -- or you can flip these around and derive one from the other
>     -- depending on your point of view.
> ...
>     -- For example, here's a similar situation where strings
>     -- come from characters...
>     --
>     type Character_Node_Type is new Node_Type with private;
> ...
>     type String_Node_Type is new Character_Node_Type with private;
> 
> and so on ...
> 
> /Jon
> 

Thanks!  That *does* make a lot more sense... I wasn't thinking OO
enough.

Anthony Jenkins
http://www.auburn.edu/~jenkian
abjenkins @ mindspring , com (Death to spammers)

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