What is Expressiveness in a Computer Language

[rossberg at ps.uni-sb.de]

Gabriel Dos Reis wrote:
> rossberg at ps.uni-sb.de writes:
>
> | Gabriel Dos Reis wrote:
> | > |
> | > | (Unfortunately, you can hardly write interesting programs in any safe
> | > | subset of C.)
> | >
> | > Fortunately, some people do, as living job.
> |
> | I don't think so. Maybe the question is what a "safe subset" consists
> | of. In my book, it excludes all features that are potentially unsafe.
>
> if you equate "unsafe" with "potentially unsafe", then you have
> changed gear and redefined things on the fly, and things that could
> be given sense before ceases to have meaning.  I decline following
> such an uncertain, extreme, path.

An unsafe *feature* is one that can potentially exhibit unsafe
behaviour. How else would you define it, if I may ask?

A safe *program* may or may not use unsafe features, but that is not
the point when we talk about safe *language subsets*.

> I would suggest you give more thoughts to the claims made in
>
>   http://www.seas.upenn.edu/~sweirich/types/archive/1999-2003/msg00298.html

Thanks, I am aware of it. Taking into account the hypothetical nature
of the argument, and all the caveats listed with respect to C, I do not
think that it is too relevant for the discussion at hand. Moreover,
Harper talks about a relative concept of "C-safety". I assume that
everybody here understands that by "safe" in this discussion we mean
something else (in particular, memory safety).

Or are you trying to suggest that we should indeed consider C safe for
the purpose of this discussion?

- Andreas