--On Monday, September 01, 2003 9:52 PM -0400 Brian McNamara
<[EMAIL PROTECTED]> wrote: [snip]
As a final aside, I think much of this thread is degenerating into
Parkinson's Bicycle Shed[*], with respect to "is it a
pointer/container/X?" At this point, I think we know what set of
methods should
On Tue, Sep 02, 2003 at 09:05:59AM +0800, Joel de Guzman wrote:
> My attempt to image "optional as conceptually a specialized but
> nevertheless, *IS-A* T, with the added specialization that it can
> be in a dead-uninitialized state." Is a feeble attempt to re-sell the idea
> of the concept that w
Mat Marcus <[EMAIL PROTECTED]> wrote:
> --On Monday, September 01, 2003 3:37 PM -0300 Fernando Cacciola
> <[EMAIL PROTECTED]> wrote:
>
>> Joel de Guzman <[EMAIL PROTECTED]> wrote in message
>>> One can think of an optional as conceptually a specialized but
>>> nevertheless, *IS-A* T, with the add
Brian McNamara <[EMAIL PROTECTED]> wrote:
> It's been pointed out before, but to re-emphasize it: from a
> type-theoretic standpoint, it is not the case that optional-isa-T.
> Rather T-isa-optional. (Dog-isa-Animal because Animal has more
> possible values.) I don't mind the suggestive conceptua
--On Monday, September 01, 2003 3:37 PM -0300 Fernando Cacciola
<[EMAIL PROTECTED]> wrote:
Joel de Guzman <[EMAIL PROTECTED]> wrote in message
One can think of an optional as conceptually a specialized but
nevertheless, *IS-A* T, with the added specialization that it can
be in a dead-uninitial
Gregory Colvin <[EMAIL PROTECTED]> wrote:
> On Monday, Sep 1, 2003, at 11:31 America/Denver, Joel de Guzman wrote:
>
>> Fernando Cacciola <[EMAIL PROTECTED]> wrote:
>>
>>> vector<>::begin returns an object with operators * and ->,
>>> yet these objects are not pointers, and once that is learned,
Fernando Cacciola <[EMAIL PROTECTED]> wrote:
>> Even if I agree with you that an optional should not be a T,
>> an optional is definitely not a pointer to T.
>>
> Definitely!
> If HTML had blinking banners I think I'd use one to state this :-)
Nor should it model a pointer. That was my point and
On Monday, Sep 1, 2003, at 11:31 America/Denver, Joel de Guzman wrote:
Fernando Cacciola <[EMAIL PROTECTED]> wrote:
vector<>::begin returns an object with operators * and ->,
yet these objects are not pointers, and once that is learned,
people do not think they are pointers.
Huh? pointer semantic
--On Monday, September 01, 2003 2:57 PM -0300 Fernando Cacciola
<[EMAIL PROTECTED]> wrote:
Mat Marcus <[EMAIL PROTECTED]> wrote in message
[snip]
After reading the documentation more carefully I learned that
optional models pointer behavior. I spelled out how the code might
look:
boost::tie(*
Joel de Guzman <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Brian McNamara <[EMAIL PROTECTED]> wrote:
> > So I completely disagree that optionals should mix the interfaces of
> > optional and the wrapped object into one. I think there should be an
> > explicit unwrapping operation
Brian McNamara <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> So I completely disagree that optionals should mix the interfaces of
> optional and the wrapped object into one. I think there should be an
> explicit unwrapping operation. But this is just my opinion, based on no
> prac
Brian McNamara <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> On Sun, Aug 31, 2003 at 12:34:39AM -0700, Mat Marcus wrote:
> [snipped]
>
> So, here's an idea for something completely new which maybe helps fit
> your requirements. I start with the motivating example:
>
>PossUninit
Mat Marcus <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> In this post I will put forward a use-case or two to help see whether
> something a little different then the current version of optional
> might be useful. I also begin making a case that a Concept like
> PossiblyUninitialize
Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> Joel de Guzman <[EMAIL PROTECTED]> wrote in message
> Direct initialization: opt = 1
> seems right since this operation is never undefined.
> This would mirror variant's interface.
Ok.
> Direct value accesing via implicit conversion: int i = opt
> s
Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> Joel de Guzman <[EMAIL PROTECTED]> wrote in message
>> There's a lot of experience with it in other languages. Why not leverage
>> that? Haskell::Maybe for instance.
>>
> Do you know of anything else besides Haskell?
No.
> I don't, and I took the t
Brian McNamara <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> On Mon, Sep 01, 2003 at 09:03:17AM +0800, Joel de Guzman wrote:
> > Do it the ref, tuple and variant way: get(). But get(), as an
> > element-access interface, should return a reference, not a pointer, as
> > it does cur
Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> vector<>::begin returns an object with operators * and ->,
> yet these objects are not pointers, and once that is learned,
> people do not think they are pointers.
Huh? pointer semantics (behavior) does not mean that they
have to be pointers.
--
J
Joel de Guzman <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Daniel Frey <[EMAIL PROTECTED]> wrote:
> > Joel de Guzman wrote:
> >> Although I don't see this as problematic:
> >>
> >> optional x;
> >> if (x)
> >> foo(x);
> >>
> >> Or perhaps:
> >>
> >> optional x
Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> First of all, let's not confuse syntax with semantics.
> optional<> HAS strict value semantics.
No it does not. The accessors have pointer behavior!
--
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net
___
Joel de Guzman <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Brian McNamara <[EMAIL PROTECTED]> wrote:
>
> > Offhand, the "pointer interface" for reading the value of an optional
> > seems good to me. Being able to say
> >
> >optional x;
> >...
> >if( x ) foo( *x );
>
Brian McNamara <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> On Sun, Aug 31, 2003 at 09:58:45AM +0800, Joel de Guzman wrote:
> > Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> > > Hi Mat,
> > >
> > > Thanks for the input.
> > >
> > > optional<> is now out on the field and it is the
Joel de Guzman <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Fernando Cacciola <[EMAIL PROTECTED]> wrote:
> > Hi Mat,
> >
> > Thanks for the input.
> >
> > optional<> is now out on the field and it is the only utility of its kind
> > I've ever seen in C++, at least in real use. This
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