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Python from Wise Guy's Viewpoint

Ingvar Mattsson ingvar at cathouse.bofh.se
Mon Oct 20 11:19:14 EDT 2003 
[ Follow-up redirected to comp.lang.lisp ]
Joachim Durchholz <joachim.durchholz at web.de> writes:

> james anderson wrote:
> 
> > Joachim Durchholz wrote:
[SNIP]
> >>I'd really like to see a Lisp dialect that valued reliability over raw
> >>expressive power. But I fear this isn't very high on the agenda of the
> >>Lisp community. Besides, it would be difficult to do that - Lisp offers
> >>no protection against peeking at internals and setting up all that
> >>unsafe-but-powerful stuff.
> > what are "internals", what is "protection"?
> 
> No way to define an opaque type. AFAIK, modern Lisps allow
> user-defined types, but they offer no way to protect them against
> inspecting their internals. I'd prefer to have at least a grain of
> information hiding...

Well... Using INSPECT one can "look inside" a type, but one has almost
the same (possibly the same) amount of introspection in (say) Python,
using dir() (and very handy it is, not as good as reading
documentation, but for those "I need to check this now" moments, it
can often be sufficient).

One should, as usual, follow one's introspective moments by checking
The Reference(s), to see if what one saw, introspecting, is
"supported" or "unsupported" (if the latter, one can bet things will
break in interesting ways, either "soon" or "on next upgarde"). But,
at times, that can be the only way to use a third-party module taht
*almost* fits one's needs.

I saw a horror-story of someone having to retro-fit third-part C++
modules by clever run-time mangling of things, to get it to work
Right, instead of "it does almost what the documentation says, but not
quite and fixing it is faster than getting a patch or rolling it
ourselves". I think it was in a thread in comp.lang.lisp, a few years
back, regarding why it was a *bad* thing forbidding access to
non-exported sympols from a package. Not exporting something is a good
sign taht one shouldn't touch it and well-behaved programmers
won't. They *may* file a bug saying "this would be handy if it was
supported", but they should, in general, not go ahead and use it.

//Ingvar
-- 
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