🚀 go-pugleaf

Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 47

In article <ksand-301292103135@wintermute.apple.com>, ksand@apple.com (Kent Sandvik ) writes:
> In article <6606.2b41845f@hayes.com>, bcoleman@hayes.com (Bill Coleman)
> wrote:
>> Sounds like you are suggesting people build frameworks in Eiffel, which
>> has formal mechanisms for defining pre and post conditions for all routines.
>> Too bad there isn't such an Eiffel implementation for the Mac.
> 
> It's not that hard to add pre- and post-conditions with methods using 
> assertions. I have my own ASSERT macro package that is conditionally
> compiled in during debug mode, and it certainly catches a lot of errors
> I would not be aware of otherwise. It's a matter of strict programming
> to add in an additional line after each error producing statement. And 
> yes indeed a language such as Eiffel helps, but it does not imply that
> you can't do the same thing using for instance macros in C/C++.

Kent,

Back on an old DOS product that since was developed by another team, I 
wrote up some C++ code that did exactly this. I found it had several limitations
that Eiffel did not.

First, the C++ macros were part of the implementation, not part of the
interface. Eiffel correctly places the pre- and post-conditions in the
interface -- since they are just as much of the specficiation of the
routines as anything else. I ended up having to move the implementation
assertions as comments in the header -- it was a lot of work to keep it up
to date and accurate.

Second, you have to rigorously add all  the macros to your code. If you 
forget one, even though you have a comment in the header -- it won't be
checked. (The assertions are more code, and hence more to debug)

Third, C++ doesn't have the recovery mechanism the Eiffel does, so
without a LOT of rigorous work in every routine, your application can only
bomb on an assertion error. (Which suffices for lots of simple conditions)

Last, it has all the appearance of a kludge. It is kinda hard to program
Eiffel in C++. It would be so much easier to program Eiffel in Eiffel.

-- 
Bill Coleman, AA4LR                ! CIS: 76067,2327    AppleLink: D1958
Principal Software Engineer        ! Packet Radio: AA4LR @ W4QO
Hayes Microcomputer Products, Inc. ! UUCP: uunet!hayes!bcoleman
POB 105203 Atlanta, GA 30348 USA   ! Internet: bcoleman%hayes@uunet.uu.net
Disclaimer: "My employer doesn't pay me to have opinions."
Quote: "The same light shines on vineyards that makes deserts." -Steve Hackett.