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Re: dynamic vs. static typing

On 2003-11-18T14:11:15-0800, Steve Dekorte wrote:
> Ok, now let's take a simple and common example such as a List that can 
> hold any collection of objects (of different types). How do we 
> implement such a thing in a statically typed system? For example, let's 
> say our List object has an "at(index)" method which returns the object 
> at the specified index. What would the return type for such a method 
> be? - without being the equivalent of a void *, in which case, we can 
> once again get "object does not respond to this message" errors, which 
> is what the static type system was supposed to prevent.

Funny how existential types keep coming up. (:

    Konstantin Läufer. 1996.  Type classes with existential types.
    Journal of Functional Programming 6(3): 485-517.

(By the way, if all you know about the List is that it contains a bunch
of objects, and if there is nothing that you can do with every object --
that is, if there is no message that every object responds to -- then
it is a pretty useless List, which you might as well replace with a
nonnegative integer.)


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