Re: Interface/Implementation (was Re: Design by Contract)

["Shmuel (Seymour J.) Metz" <nospam@gsg.eds.com>]

Robert Dewar wrote:
> 
> Don said
> 
> <<Frankly, if I were to have forced dependency ordering inflicted on me but
> could choose which scheme, I would choose *reverse* dependency ordering.
> At least then I could read listings in a sensible order - from high-level to
> low-level.>>
> 
> Can you clarify your experience with Ada here. it is sounding more and more
> as though you are talking from imagination rather than experience.

Although I find the ordering requirements in Ada to be a nuisance, I
have to
agree with you that the specifications should be done before the body.
In all
of the Ada that I wrote, the specifications had to pass a design review
before we
were allowed to start writing the body, and everything that I saw
convinced me
that not only was the requiring reasonable but that it was necessary.

In an earlier article you drew an anology with reading a book. Well, I
read
novels in a linear fashion, but I skip around in text books. In
particular,
technical literature frequently refers the reader to an appendix for
details. I 
believe that most people read code the same way: the choice of what to
read and 
in what order depends on what they are attempting to learn.

In language with an arbitrary declaration order, I find the declarations
at the 
end more often than the beginning. In some cases the code is more
readable if the 
declarations are split. The acid test is to throw it at someone who's
never seen
it before and see if he has trouble understanding it.

I can't comment on Eiffel, but I definitely consider Ada to be more
readable and
maintainable than C, Pascal or FORTRAN.

-- 

                        Shmuel (Seymour J.) Metz
                        Senior Software SE

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