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

[doylep@ecf.toronto.edu (Patrick Doyle)]

In article <34104798.17D7@pseserv3.fw.hac.com>,
W. Wesley Groleau x4923 <wwgrol@pseserv3.fw.hac.com> wrote:
>
>> [I said:]
>> 
>>   What do you mean by "enforced"?  How could they be any more 
>> "enforced" than to either be or not be included in the short form?  
>> How can the compiler tell what kind of comments you are adding if 
>> you add them wrong?
>
>That's the point.  The implication has been made that certain types
>of comments are needed in the short form, and to get them there, one
>has to follow some rule which has not been stated in this thread.
>
>Whereas if the spec is a truly separate item (not generated by a tool)
>any comments it has (right or wrong) can not be omitted by the
>non-existent extraction process.  Nor can the non-existent extraction 
>process add something from the implementation.

I see what you mean.  This is true.  However, remember that in order
for comments to appear in the interface file, the programmer must
put them *there* instead of the implementation file.  If this seems
trivial to you, then good, because I think it's trivial too.  But so
is putting the comments in the right place in Eiffel.

It looks like this:

class Goober
  feature Puree is
        -- Comments describing the interface
    do
        -- Comments describing the implementation
    end
end

See, the interface comments still appear in the interface, and the
implementation comments still appear in the implementation.  It's
just that they're in the same file now.

So whatever miniscule amount of mental discipline is necessary to put
comments in the right place in Ada applies to Eiffel too.

(BTW, I hope I got the comment placement right--I've never used the
short tool!)

 -PD
-- 
--
Patrick Doyle
doylep@ecf.utoronto.ca