Re: [Caml-list] Delegation based OO

[Kenneth Knowles <kknowles@berkeley.edu>]

> class *type* does_something = object ... end
> 
> class does_more (an_object:#does_something) = object
>    delegates an_object
>    ...
> end
> 
> "an_object" may have a method, say, "an_object#foo : int".
> "does_more" could overwrite the method, and define "does_more#foo :
> float".  Now, what type should "self#pooh" have in the definition of
> an_object?

This is a type error, just as if you override a class method with one of a
different type:

# class x = object method y = 3 end;;
class x : object method y : int end
# class y = object inherit x method y = 4 end;;
class y : object method y : int end
# class z = object inherit x method y = "hello" end;;
This expression has type string but is here used with type int

The same strictness could be applied to delegation.

Kenn

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