RE: (off-topic) RE: [Doxygen-users] Documenting IDL

[Victor A. W. Jr. <va...@ru...>]

or use void* like I ORIGINALLY suggested (and is suggested by looking at 
how the STL does it with iterators.

At Monday 2001/06/11 09:37, you wrote:

> > -----Original Message-----
> > From: dox...@li...
> > [mailto:dox...@li...]On Behalf Of Hendrik
> > Schober
> > Sent: 10 June 2001 20:58
> > To: dox...@li...
> > Subject: Re: (off-topic) RE: [Doxygen-users] Documenting IDL
> >
> >
> > "Stephen Goudge" <ste...@pi...> wrote:
> >
> > > [...]
> > > I did originally have an operator int() that could be used
> > in if-statements,
> > > which worked fine using VC++2 through to VC++4; then a
> > client bought VC++5 and
> > > it became ambiguous (I forget the precise reason why), so
> > everything switched to
> > > IsValid() from then on.
> >
> >   'int' seems like one of the most troublesome ideas.
> >   (What's 'spa+spb' to become then?)
> >
> > > [...]
> > > Even with a decent compiler, there is the vexed question of
> > what the cast
> > > operator should be casting _to_ - you don't really want to
> > return another
> > > pointer type, as that looks too much like you're providing
> > a backdoor. These
> > > days, 'bool' would be a reasonable choice (now that the
> > compilers actually
> > > support 'bool'). The best choice would be the mythical
> > 'logical' type that 'if',
> > > 'while' etc use, but that isn't available :-(
> >
> >   Oh, but that's available: It's named 'bool'.
>
>The "the mythical 'logical' type that 'if', 'while' etc use" is not 'bool' - I
>suppose you could produce a parser that used bool there, but just taking a 
>straw
>poll around the office, the guy sitting next to me (working on a C compiler)
>uses 'long int' for 'if' etc, which is what the Standard says you do 
>(hence the
>use of operator int() to feed 'if' in the oldest code). Meanwhile, in my
>program, a C-expression evaluator has a type 'logical' that is only used
>internally (ie, from the point of view of someone writing an expression to be
>evaluated, is mythical because you can not declare anything to have type
>'logical') and lives at the very opposite end of the automatic type promotion
>ladder from 'bool'.
>
>Also, unfortunately, all that time ago, 'bool' was not available in all the
>compilers being used :-(
>
> >   But 'bool' isn't all that good either, because it's an
> >   arithmetic type. (Or was it convertible into one?)
> >   You could thus write 'sp+5' and get funny results.
>
><snip>
>
>That points out the problem exactly - all of the types that you can use here
>already have well-known meanings and tend to imply that it is possible to use
>them in expressions _other_ than just 'if'. No matter what you choose, you can
>write something that will give funny results.
>
>Hence (not to be taken too seriously) wish to be able to use a type, 
>'logical',
>that does not carry any such baggage, based on the fact that I _know_ such a
>type does/can live deep within the bowels of a compiler.
>
>The _only_ answer I know of that is possible to implement _and_ totally 
>free of
>any such baggage is an "IsValid()" method - which is right back to where we
>started.
>
> >   In his book "Modern C++ Design" Andrei Alexandrescu
> >   discusses this issue. His idea (typing from memory):
> >
> >   template<class T>
> >   class SmartPtr {
> >     private:
> >       class Tester {
> >         void operator delete(void*);
> >       };
> >     public:
> >       operator Tester*() const
> >       {
> >         if( !IsValid() )
> >           return NULL;
> >         static Tester tester;
> >         return tester;
> >       }
> >       // ...
> >   };
> >
> >   (The private 'operator delete()' is there to prevent
> >   users from trying to delete the result of calling the
> >   convertion operator.)
> >
> >   I have not used this yet, so I don't know whether it's
> >   really as great an idea as it seemed to me.
> >
> > > Stephen Goudge
> >
> >   Schobi
>
>Aha, yet another approach :-)
>
>The suggestions - _all_ of them - all have their merits and all can all work
>extremely well, but, just like the search the One True String Class, there 
>is no
>absolute best answer to this. Shame really.
>
>Now, back to Doxygen...
>
>Stephen Goudge
>
>
>
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Victor A. Wagner, Jr.
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