Hello everyone,


I am reading the C++ Programming Language book, but can not find the
function of explicit keyword of constructor. Could anyone explain its
usage or refer some learning materials please?


thanks in advance,
George

George2 wrote:
> I am reading the C++ Programming Language book, but can not find the
> function of explicit keyword of constructor. Could anyone explain its
> usage or refer some learning materials please?

Have you tried googling?

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

* Victor Bazarov:
> George2 wrote:
>> I am reading the C++ Programming Language book, but can not find the
>> function of explicit keyword of constructor. Could anyone explain its
>> usage or refer some learning materials please?
>
> Have you tried googling?

One problem with googling is that the FAQ confuses explicit constructor
calls with placement new syntax.

Short of it, "explicit" on a converting constructor suppresses all
implicit calls of that constructor, so that all calls must be explicit.

This s avoid silly automatic conversions such as the compiler
accepting assignment of integer 666 to myVector, treating it as myVector
= std::vector<SomeType>(666) -- if you want that, you'll have to write
it explicitly, as shown here. Disclaimer: I haven't checked whether
that std::vector constructor is "explicit". I assume it is.

Cheers, & hth.,

- Alf

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

In article
<ea06618a-5a8e-419e-8ff2-a1261f2d2169@e23g2000prf.googlegroups.com>,
George2 <george4academic@yahoo.com> wrote:

> Hello everyone,
>
>
> I am reading the C++ Programming Language book, but can not find the
> function of explicit keyword of constructor. Could anyone explain its
> usage or refer some learning materials please?
>
>
> thanks in advance,
> George

The "explicit" keyword is defined in 12.3.1:

"An explicit constructor constructs objects just like non-explicit
constructors, but does so only where the
direct-initialization syntax (8.5) or where casts (5.2.9, 5.4) are
explicitly used."

In other words, implicit conversion of the constructor's parameter is
turned off when a constructor is declared explicit.

-dr

On Mon, 10 Dec 2007 22:00:36 -0800 (PST) in comp.lang.c++, George2
<george4academic@yahoo.com> wrote,
>I am reading the C++ Programming Language book, but can not find the
>function of explicit keyword of constructor.

Section 11.7.1

George2 wrote:
> Hello everyone,
>
>
> I am reading the C++ Programming Language book, but can not find the
> function of explicit keyword of constructor.

Have you tried the index?

--
Ian Collins.