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From: Vladimir Batov <vb.mail.247@gmail.com>
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Subject: Re: optional<T>, one more value or two states
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On Saturday, January 26, 2013 10:22:11 AM UTC+11, Nicol Bolas wrote:
>
> On Friday, January 25, 2013 2:09:20 PM UTC-8, Tony V E wrote:
>>
>> On Fri, Jan 25, 2013 at 3:20 PM, Nicol Bolas <jmck...@gmail.com> wrote: 
>> > ... 
>> Do you think we should back away from all the pointer-ish interface 
>> parts and move more towards container-ish?  
>>
>
"We" are reading the 3rd revision of the document describing the facility 
which has been in heavy use for a while and which has already been 
submitted for standardization. "we should back away from all the 
pointer-ish interface"... Is it a serious question or a tease?
 
 

> No it should not. I'm not particularly enamoured with `operator*`, but 
> `operator[]` makes no sense at all. Why not just `value` (or `get` for 
> those who like that)? Do we really need an operator at all?
>

Uhm, because we need to dereference 'optional' and the language has a 
dereferencing operator (op*) which happens to be used everywhere else to 
dereference.  
 

> There is no "all the pointer-ish interface"; there's only `operator*. 
> That's the only part of optional that is like a pointer (OK, the `explicit 
> operator bool` too, but that's hardly unique to pointers); everything else 
> works differently from pointers.
>

There is nothing "pointer-ish" about the operator called a dereferencing 
operator. Customization (oveloading) of that op* together with the other 
dereferencing op->() is "important to a class of interesting programs" (as 
Stroustrup puts it). Indeed, that interface (as many other concepts) has 
been borrowed from C where these operators worked with pointers and C++ 
intentionally preserves C syntactic flavor. It does not make pointers claim 
"ownership" of these operators. These operators are the standard interface 
for the whole family of classes implementing the proxy concept/pattern... 
and the pointer is just one -- the most basic and primitive -- 
implementation of that concept. 
 

-- 

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On Saturday, January 26, 2013 10:22:11 AM UTC+11, Nicol Bolas wrote:<blockq=
uote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-lef=
t: 1px #ccc solid;padding-left: 1ex;">On Friday, January 25, 2013 2:09:20 P=
M UTC-8, Tony V E wrote:<blockquote class=3D"gmail_quote" style=3D"margin:0=
;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex">On Fri, Jan=
 25, 2013 at 3:20 PM, Nicol Bolas &lt;<a>jmck...@gmail.com</a>&gt; wrote:
<br>&gt; ...
<br>
Do you think we should back away from all the pointer-ish interface
<br>parts and move more towards container-ish?&nbsp; <br></blockquote></blo=
ckquote><div><br>"We" are reading the 3rd revision of the document describi=
ng the facility which has been in heavy use for a while and which has alrea=
dy been submitted for standardization. "we should back away from all the po=
inter-ish interface"...
Is it a serious question or a tease?<br>&nbsp;<br></div><div>&nbsp;</div><b=
lockquote class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;borde=
r-left: 1px #ccc solid;padding-left: 1ex;"><blockquote class=3D"gmail_quote=
" style=3D"margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-le=
ft:1ex"></blockquote><div>No it should not. I'm not particularly enamoured =
with `operator*`, but `operator[]` makes no sense at all. Why not just `val=
ue` (or `get` for those who like that)? Do we really need an operator at al=
l?<br></div></blockquote><div><br>Uhm, because we need to dereference 'opti=
onal' and the language has a dereferencing operator (op*) which happens to =
be used everywhere else to dereference.&nbsp; <br>&nbsp;</div><blockquote c=
lass=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-left: 1px=
 #ccc solid;padding-left: 1ex;"><div>There is no "all the pointer-ish inter=
face"; there's only `operator*. That's the only part of optional that is li=
ke a pointer (OK, the `explicit operator bool` too, but that's hardly uniqu=
e to pointers); everything else works differently from pointers.<br></div><=
/blockquote><div><br>There is nothing "pointer-ish" about the operator call=
ed a dereferencing operator. Customization (oveloading) of that op* togethe=
r with the other dereferencing op-&gt;() is "important to a class of intere=
sting programs" (as Stroustrup puts it). Indeed, that interface (as many ot=
her concepts) has been borrowed from C where these operators worked with po=
inters and C++ intentionally preserves C syntactic flavor. It does not make=
 pointers claim "ownership" of these operators. These operators are the sta=
ndard interface for the whole family of classes implementing the proxy conc=
ept/pattern... and the pointer is just one -- the most basic and primitive =
-- implementation of that concept. <br>&nbsp;</div><br>

<p></p>

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&nbsp;<br />

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