From: Dave Thomas <Dave@...>
Date: 2000-06-21T14:00:11-05:00
Subject: [ruby-talk:03590] Re: Static Typing( Was: Waffling between Python and Ruby)


olczyk@interaccess.com (Thaddeus L. Olczyk) writes:

> On 21 Jun 2000 12:10:18 -0500, Dave Thomas <Dave@Thomases.com> wrote:
> 
> >> Maybe I was misunderstanding the original poster, but he seemed to be
> >> advocating DbC without any notion of types other than "object that responds
> >> to message X".  To state the obvious, if the language has a notion of
> >> interface, protocol, or type, it's merely necessary to check that the object
> >> conforms to that type, at compile-time or run-time, since the contract is
> >> available in the interface/protocol/type definition.
> >
> >Not always (there are issues with polymorphism) but in general.
> There are no issues with polymorphism. This is what polymorphism
> is all about. Yes there are programmers that can create issues ( eg by
> violating Liskov ), but there are no *good* programmers.

OK - I understand.

There's no need for any system of contract checking to be rigorous,
because we can rely on *good* programmers to follow the rules such as
LSP.

Wonder why we need contracts at all ;-)


DbC is a good discipline, but it does not *ensure* correctness. Anyone 
who codes as if it does is risking ignoring real problems.


Regards


Dave