gennaro_prota@my-deja.com wrote:

> Clause 12.3.1 of the standard provides the following rules/definitions:

> 3. A copy-constructor (12.8) is a converting constructor. An implicitly-
>    declared copy constructor is not an explicit constructor; it may be
>    called for implicit type conversions.

Hum. This reminds me of something I have never quite understoud:

- What's a converting copy constructor ?

- What's a converting default constructor ?

Are these animals the results of uncontrolled C++ genetic
experiments, the inventions of a psychopathic committee
member, or useful tools that are simply beyond my C++
knowledge ?

--
Valentin Bonnard

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On Mon, 12 Feb 2001 17:04:52 GMT, Valentin.Bonnard@free.fr (Valentin
Bonnard) wrote:

> gennaro_prota@my-deja.com wrote:
>
> > Clause 12.3.1 of the standard provides the following rules/definitions:
>
> > 3. A copy-constructor (12.8) is a converting constructor. An implicitly-
> >    declared copy constructor is not an explicit constructor; it may be
> >    called for implicit type conversions.
>
> Hum. This reminds me of something I have never quite understoud:

Half seriously:

12.3.1/1 defines a converting ctor as one without the
explicit word and usable with one arguement.

> - What's a converting copy constructor ?

struct S { S (); S (S const&); };
struct T : S { int t; };
T t;
t.t = 42;
S s(t);

Does the slicing qualify as a conversion?  Clause 13 states that there
is no derived to base conversion.  I guess it is a converting ctor
because it performs the standard identity conversion.

> - What's a converting default constructor ?

There is no such thing, but it may still be explicit.  Maybe because:

struct S { int s; explicit S (int i = 42); };

The one constructor is both a converting ctor and a default ctor.

S s1;     // valid
S s2 = 7; // invalid

> Are these animals the results of uncontrolled C++ genetic
> experiments, the inventions of a psychopathic committee
> member, or useful tools that are simply beyond my C++
> knowledge ?

All of the above?

What does explicit mean on a ctor with two required parameters mean?
I think, nothing.  It is easiest to just allow it on any ctor?

John

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