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From: "Harald Korneliussen" <vintermann@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: What is wrong with Ada?
Date: 13 Apr 2007 01:55:59 -0700
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On Apr 12, 8:47 pm, Robert A Duff <bobd...@shell01.TheWorld.com>
wrote:
> There is no way to be sure the code is bug free!  Not in any language.
> Not using testing, nor any other method (including so-called
> proof of correctness).
>
In so-called dependently-typed languages, you can use the type system
to ensure the correctness of a program, at least such a program as
your primality checker. The type-theorists talk about this curry-
howard isomorphism thing, which apparently is an isomorphism between
programs and proof.

I think the SPARK people would agree that there are indeed methods to
assure that code is bug-free, at least to the extent that the
specification is bug-free (and even that can to some degree be checked
mechanically!). Not to say that it is easy, cheap, or even feasible in
very many cases, but don't you underestimate a good type system.