Re: c++ "with" keyword

[Tolga Dalman <ates100@web.de>]

On Sat, 04 Jan 2003 09:31:50 -0800 Gianni Mariani <gmariani@chaincast.com> wrote:

> Andrew Haley wrote:
> 
> >Momchil Velikov writes:
> > > >>>>> "Robert" == Robert Dewar <dewar@gnat.com> writes:
> > > 
> > >     Robert> If you think "with" is valuable, then the task is to
> > >     Robert> convince the guardians of the C++ standard of this. If
> > >     Robert> you can't convince the
> > > 
> > > Not related to this particular "with" discussion, but I couldn't
> > > disagree more.  A standards body should not invent language
> > > "features", but rather codify existing (proven) extensions.
> >
> >I totally agree.  A standards should not invent language features, or
> >-- heaven forbid -- programming languages.  The reason for this is
> >pretty obvious, in that once a feature is standardized it's too late
> >to remove it if it has some fatal flaw.
> >  
> >
> I agree as well.
> 
> Proposals of language extensions should come from anyone :)  The metrits 
> discussed in community and accepted as a standard once it is generally 
> accepted.
> 
> So, I'd like to steer the discussion back to the merits of "with".
> 
> The "with" syntax was a pain in the rear in Pascal and I never want to 
> see it again - this is why:
> 
> Take 2 structures, A and B which are both used in a "with" statement.
> 
> e.g. (I'll use the proposed new "with" syntax in c++ below)
> 
> Let's start with some valid working code ...
> 
> struct A {
>     int    X;
>     int    Y;
>     int    hUgH;
> };
> 
> struct B {
>     int    Z;
> };
> 
> int func()
> {
>         ....
>         A & a;
>         B & b;
>         ....
> 
>         with ( a )
>         witb ( b )
>         {
> 
>             Y = Z;
>             hUgH = X; //  woz this then eh ? <-- point of confusion
>         }
>         ...
> }
> 
> And a little later someone comes and fixes a bug and adds
> 
> struct B {
>     int    Z;
>     int    X;    // need an X to fix The Bug (tm)
> };
> 
> Oops - which X is now instantiated at "point of confusion" ?
> 
> Someone innocently added a new member and completly changed the 
> behaviour of the code.  For code maintainability, I'd suggest that this 
> would cause more difficult to discover problems than would be merited.
> 

it should be possible to disallow a "with" keyword within another "with" block.

> This is also one of the reasons I don't like namespaces much either - 
> hence I allways prefix identifiers that are not within a class's scope.
> 

hm, i know a lot of people who don't like namespaces aswell, but the point is: 
it'd be great to have a compiler-feature to make code more readable. 
i think, long struct-names are very annoying and a common  solution 
(either standard or compiler-addon) for this problem would be very good.
just my opinion. 

> If you were to implement (heaven forbid) the "with" mechanism, I'd 
> suggest you use the "using" keyword instead.
>

the actual name doesn't matter i think, but "with" is already used in other programming languages. so, why to use "using"?
 

brg, 
Tolga Dalman.