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Re: Converting constructors
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Bonita Montero
Nov 25, 2016, 5:31:47 AM11/25/16
to
Am 25.11.2016 um 11:09 schrieb Stefan Ram:
> - one argument
> but
> - no "explicit".
It is one arguemnt *and* no explicit.
--
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> - one argument
> but
> - no "explicit".
It is one arguemnt *and* no explicit.
--
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Alf P. Steinbach
Nov 25, 2016, 11:17:35 AM11/25/16
to
On 25.11.2016 11:09, Stefan Ram wrote:
> IIRC, the C++ primer says that a converting constructor is a
> constructor that accepts exactly one argument. It says that
> constructors with more arguments can not possibly be considered
> for conversions, because a conversion situation only is given
> in the case of a single value.
>
> However, we all know 12.3.1p1 (now not from the primer,
> but from a recent draft of the standard):
>
> »A constructor declared without the function-specifier
> explicit specifies a conversion from the types of its
> parameters (if any) to the type of its class. Such a
> constructor is called a converting constructor.« .
>
> So, today's definition of »converting constructor« is not
> converting constructor is a constructor that accepts a single
> argument, why has the standard dropped this requirement?
>
[code]
struct A
{
A( int, int ) {}
};
struct B
{
explicit B( int, int ) {}
};
auto main() -> int
{
A a = {1, 2};
B b = {1, 2}; //! Nyet, constructor is explicit.
}
[/code]
Cheers & hth.,
- Alf
> IIRC, the C++ primer says that a converting constructor is a
> constructor that accepts exactly one argument. It says that
> constructors with more arguments can not possibly be considered
> for conversions, because a conversion situation only is given
> in the case of a single value.
>
> However, we all know 12.3.1p1 (now not from the primer,
> but from a recent draft of the standard):
>
> »A constructor declared without the function-specifier
> explicit specifies a conversion from the types of its
> parameters (if any) to the type of its class. Such a
> constructor is called a converting constructor.« .
>
> So, today's definition of »converting constructor« is not
>
> - one argument
>
> but
>
> - no "explicit".
>
> But after the C++ primer has so convincingly explained why a
> - one argument
>
> but
>
> - no "explicit".
>
> converting constructor is a constructor that accepts a single
> argument, why has the standard dropped this requirement?
>
[code]
struct A
{
A( int, int ) {}
};
struct B
{
explicit B( int, int ) {}
};
auto main() -> int
{
A a = {1, 2};
B b = {1, 2}; //! Nyet, constructor is explicit.
}
[/code]
Cheers & hth.,
- Alf
Alf P. Steinbach
Nov 25, 2016, 11:19:40 AM11/25/16
to
I think it's just some committee member's wet dream, to be able to
answer questions like this.
Possibly.
Cheers!,
- Alf
Bonita Montero
Nov 25, 2016, 12:06:39 PM11/25/16
to
Am 25.11.2016 um 17:14 schrieb Alf P. Steinbach:
> B b = {1, 2}; //! Nyet, constructor is explicit.
This is not converting operation.
> B b = {1, 2}; //! Nyet, constructor is explicit.
--
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Alf P. Steinbach
Nov 25, 2016, 12:09:05 PM11/25/16
to
On 25.11.2016 18:06, Bonita Montero wrote:
> Am 25.11.2016 um 17:14 schrieb Alf P. Steinbach:
>
>> B b = {1, 2}; //! Nyet, constructor is explicit.
>
> This is not converting operation.
Well, you're entitled to your opinion about what labels fit, but I for
> Am 25.11.2016 um 17:14 schrieb Alf P. Steinbach:
>
>> B b = {1, 2}; //! Nyet, constructor is explicit.
>
> This is not converting operation.
one am not very interested in that.
So, I suggest you refrain from entirely meaningless commentary, a.k.a.
babble, in this group, unless it concerns swearing or sausages.
Thank you.
Cheers!
- Alf
Bonita Montero
Nov 25, 2016, 12:20:36 PM11/25/16
to
Am 25.11.2016 um 18:06 schrieb Alf P. Steinbach:
>>> B b = {1, 2}; //! Nyet, constructor is explicit.
>> This is not converting operation.
> ... refrain from entirely meaningless commentary, ...
>>> B b = {1, 2}; //! Nyet, constructor is explicit.
>> This is not converting operation.
This is not meaningless.
The code you show doesn't show any comversion.
--
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Alf P. Steinbach
Nov 25, 2016, 12:30:50 PM11/25/16
to
On 25.11.2016 18:20, Bonita Montero wrote:
> Am 25.11.2016 um 18:06 schrieb Alf P. Steinbach:
>>>> B b = {1, 2}; //! Nyet, constructor is explicit.
>
>>> This is not converting operation.
>
>> ... refrain from entirely meaningless commentary, ...
>
> This is not meaningless.
> The code you show doesn't show any comversion.
Apart from your opinion about labels, which I'll not contest (any person
> Am 25.11.2016 um 18:06 schrieb Alf P. Steinbach:
>>>> B b = {1, 2}; //! Nyet, constructor is explicit.
>
>>> This is not converting operation.
>
>> ... refrain from entirely meaningless commentary, ...
>
> This is not meaningless.
> The code you show doesn't show any comversion.
is free to choose his or her own terminology, no matter how impractical
it may be, no matter how undefined or meaningless),
do you think it's relevant to the OP's question that the `explicit`
constructor prevents that line from compiling?
Cheers!,
- Alf
Bonita Montero
Nov 25, 2016, 12:34:14 PM11/25/16
to
Am 25.11.2016 um 18:27 schrieb Alf P. Steinbach:
> do you think it's relevant to the OP's question that the
> `explicit` constructor prevents that line from compiling?
The code you postet is absoltuely useless for the question
> do you think it's relevant to the OP's question that the
> `explicit` constructor prevents that line from compiling?
Stefan Ram asked because it doesn't show any conversion
-operation.
--
http://facebook.com/bonita.montero/
Alf P. Steinbach
Nov 25, 2016, 2:13:36 PM11/25/16
to
On 25.11.2016 18:34, Bonita Montero wrote:
> Am 25.11.2016 um 18:27 schrieb Alf P. Steinbach:
>
>> do you think it's relevant to the OP's question that the
>> `explicit` constructor prevents that line from compiling?
>
> The code you postet is absoltuely useless for the question
> Stefan Ram asked because it doesn't show any conversion
> -operation.
Well, that's just idiocy.
> Am 25.11.2016 um 18:27 schrieb Alf P. Steinbach:
>
>> do you think it's relevant to the OP's question that the
>> `explicit` constructor prevents that line from compiling?
>
> The code you postet is absoltuely useless for the question
> Stefan Ram asked because it doesn't show any conversion
> -operation.
- Alf
Bonita Montero
Nov 25, 2016, 2:28:36 PM11/25/16
to
Am 25.11.2016 um 20:10 schrieb Alf P. Steinbach:
>> The code you postet is absoltuely useless for the question
>> Stefan Ram asked because it doesn't show any conversion
>> -operation.
> Well, that's just idiocy.
Stefan asked why the standad doesn't make a clear statement about
>> The code you postet is absoltuely useless for the question
>> Stefan Ram asked because it doesn't show any conversion
>> -operation.
> Well, that's just idiocy.
what a converting constructor is except specifying that it might
not be explicit. For that question you don't give any clarification
with your code because it doesn't show any conversion.
--
http://facebook.com/bonita.montero/
Alf P. Steinbach
Nov 25, 2016, 2:39:21 PM11/25/16
to
Cheers!,
- Alf
Bonita Montero
Nov 25, 2016, 2:53:41 PM11/25/16
to
Am 25.11.2016 um 20:36 schrieb Alf P. Steinbach:
>> Stefan asked why the standad doesn't make a clear statement about
>> what a converting constructor is except specifying that it might
>> not be explicit. For that question you don't give any clarification
>> with your code because it doesn't show any conversion.
> Repeating the idiocy doesn't make it meaningful.
My objection isn't idiocy, but yours. Because the code you supplied
>> Stefan asked why the standad doesn't make a clear statement about
>> what a converting constructor is except specifying that it might
>> not be explicit. For that question you don't give any clarification
>> with your code because it doesn't show any conversion.
> Repeating the idiocy doesn't make it meaningful.
doesn't clarify the question Stefan asked for. It simply has nothing
to do with the question.
--
http://facebook.com/bonita.montero/
Alf P. Steinbach
Nov 25, 2016, 3:26:19 PM11/25/16
to
idiocy, you're trolling, waiting for someone else to join in and then
accept their explanation as if I hadn't been clear enough.
In the posting I'm replying you changed newsgroups to
`de.alt.gruppenkasper`, and that's also typical trolling behavior.
Plonk.
Or if you don't get that, please do fuck off.
- Alf
Louis Krupp
Nov 25, 2016, 3:30:06 PM11/25/16
to
On 25 Nov 2016 10:09:48 GMT, r...@zedat.fu-berlin.de (Stefan Ram)
C++11:
http://en.cppreference.com/w/cpp/language/converting_constructor
Louis
wrote:
> IIRC, the C++ primer says that a converting constructor is a
> constructor that accepts exactly one argument. It says that
> constructors with more arguments can not possibly be considered
> for conversions, because a conversion situation only is given
> in the case of a single value.
>
> However, we all know 12.3.1p1 (now not from the primer,
> but from a recent draft of the standard):
>
> »A constructor declared without the function-specifier
> explicit specifies a conversion from the types of its
> parameters (if any) to the type of its class. Such a
> constructor is called a converting constructor.« .
>
> So, today's definition of »converting constructor« is not
>
> - one argument
>
> but
>
> - no "explicit".
>
> But after the C++ primer has so convincingly explained why a
> converting constructor is a constructor that accepts a single
> argument, why has the standard dropped this requirement?
According to this page, the single-argument requirement went away with
> IIRC, the C++ primer says that a converting constructor is a
> constructor that accepts exactly one argument. It says that
> constructors with more arguments can not possibly be considered
> for conversions, because a conversion situation only is given
> in the case of a single value.
>
> However, we all know 12.3.1p1 (now not from the primer,
> but from a recent draft of the standard):
>
> »A constructor declared without the function-specifier
> explicit specifies a conversion from the types of its
> parameters (if any) to the type of its class. Such a
> constructor is called a converting constructor.« .
>
> So, today's definition of »converting constructor« is not
>
> - one argument
>
> but
>
> - no "explicit".
>
> But after the C++ primer has so convincingly explained why a
> converting constructor is a constructor that accepts a single
> argument, why has the standard dropped this requirement?
C++11:
http://en.cppreference.com/w/cpp/language/converting_constructor
Louis
Alf P. Steinbach
Nov 25, 2016, 3:35:22 PM11/25/16
to
asked why, literally, as the last you quoted, "why has the standard
dropped this [single argument] requirement". I.e. what impact does it have.
As far as I know the only impact is for copy initialization syntax with
curly braces initializer, as I've already exemplified.
Mr Flibble
Nov 25, 2016, 3:40:07 PM11/25/16
to
is from an initializer list.
/Flibble
Bonita Montero
Nov 25, 2016, 3:50:45 PM11/25/16
to
Am 25.11.2016 um 21:39 schrieb Mr Flibble:
> Mate, you are making a tit of yourself.
> Alf is correct: the conversion is from an initializer list.
Construction via initializer-list isnt a conversion.
> Mate, you are making a tit of yourself.
> Alf is correct: the conversion is from an initializer list.
--
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Bonita Montero
Nov 25, 2016, 3:58:51 PM11/25/16
to
Am 25.11.2016 um 21:50 schrieb Bonita Montero:
> Construction via initializer-list isnt a conversion.
Or to be more pecise: conversion is when there is a new object generated
> Construction via initializer-list isnt a conversion.
through a constructor or a type-conversion operator from from another
object. That's not the case with Alf's code. There isnt a second object.
--
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Mr Flibble
Nov 25, 2016, 3:58:55 PM11/25/16
to
On 25/11/2016 20:50, Bonita Montero wrote:
> Am 25.11.2016 um 21:39 schrieb Mr Flibble:
>
>> Mate, you are making a tit of yourself.
>> Alf is correct: the conversion is from an initializer list.
>
> Construction via initializer-list isnt a conversion.
Yes, in this case it is.
> Am 25.11.2016 um 21:39 schrieb Mr Flibble:
>
>> Mate, you are making a tit of yourself.
>> Alf is correct: the conversion is from an initializer list.
>
> Construction via initializer-list isnt a conversion.
/Flibble
Mr Flibble
Nov 25, 2016, 4:00:26 PM11/25/16
to
On 25/11/2016 20:58, Bonita Montero wrote:
> Am 25.11.2016 um 21:50 schrieb Bonita Montero:
>
>> Construction via initializer-list isnt a conversion.
>
> Or to be more pecise: conversion is when there is a new object generated
> through a constructor or a type-conversion operator from from another
> object. That's not the case with Alf's code. There isnt a second object.
Mate, have you ever heard the phrase "digging yourself into a hole"?
> Am 25.11.2016 um 21:50 schrieb Bonita Montero:
>
>> Construction via initializer-list isnt a conversion.
>
> Or to be more pecise: conversion is when there is a new object generated
> through a constructor or a type-conversion operator from from another
> object. That's not the case with Alf's code. There isnt a second object.
/Flibble
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