Literal operator templates

[Inconnu]

In the new standard the literal operator templates are restricted to
have a single non-type template parameter of type char which is a
pack. This restriction makes illegal the following construction for
binary integer literals:

template<char C0, char ...C>
constexpr unsigned long long operatorl "" b ()
{
static_assert (C0 == '0' || C0 == '1');
return sizeof... (C) == 0 ? C0 - '0' : ((C0 - '0') << sizeof...
(C)) + operator "" b<C...> ();
}

I think it would be better to require instead that all template
parameters be non-type parameters of type char, while the last of them
may be a parameter pack.

 

[Johannes Schaub (litb)]

In the new standard the literal operator templates are restricted to
have a single non-type template parameter of type char which is a
pack. This restriction makes illegal the following construction for
binary integer literals:

template<char C0, char ...C>
constexpr unsigned long long operatorl "" b ()
{
static_assert (C0 == '0' || C0 == '1');
return sizeof... (C) == 0 ? C0 - '0' : ((C0 - '0') << sizeof...
(C)) + operator "" b<C...> ();
}

I think it would be better to require instead that all template
parameters be non-type parameters of type char, while the last of them
may be a parameter pack.

The shown definition would be illegal anyway, because there is no template
to use for `operator "" b<>` .

Can you show an example where it would be clearly advantageous?

 

[Inconnu]

The shown definition would be illegal anyway, because there is no template
to use for `operator "" b<>` .

Can you show an example where it would be clearly advantageous?

Can you show an example where `operator "" b<>` is used?

 

[Inconnu]

The shown definition would be illegal anyway, because there is no template
to use for `operator "" b<>` .

Can you show an example where it would be clearly advantageous?

Can you show an example where `operator "" b<>` is used?

 

[Inconnu]

 Can you show an example where `operator "" b<>` is used?

I understood. The `operator "" b<>` is required when types of
expressions are calculated. Then my example may be changed so:

template<char ...C> unsigned long long operator "" b();

template<char C0, char ...C>
constexpr unsigned long long operatorl "" b ()
{
static_assert (C0 == '0' || C0 == '1');
return sizeof... (C) == 0 ? C0 - '0' : ((C0 - '0') << sizeof...
(C)) + operator "" b<C...> ();

}

 

[Inconnu]

Or even better variant, which doesn't refer to `operator "" b<>`
(which by itself, from the literal, can't be evoked, because character
sequence of a user-defined-literal always contains at least 1
element):

template<char C0, char ...C>
constexpr unsigned long long operatorl "" b ()
{
static_assert (C0 == '0' || C0 == '1');
return ((C0 - '0') << sizeof... (C)) + operator "" b<C...> ();

}

template<char C0>
constexpr unsigned long long operatorl "" b ()
{
static_assert (C0 == '0' || C0 == '1');
return ((C0 - '0');
}

 

[Leo Equinox Gaspard]

Le 06/07/2011 17:53, Inconnu a écrit :

In the new standard the literal operator templates are restricted to
have a single non-type template parameter of type char which is a
pack. This restriction makes illegal the following construction for
binary integer literals:

template<char C0, char ...C>
constexpr unsigned long long operatorl "" b ()
{
static_assert (C0 == '0' || C0 == '1');
return sizeof... (C) == 0 ? C0 - '0' : ((C0 - '0')<< sizeof...
(C)) + operator "" b<C...> ();
}

I think it would be better to require instead that all template
parameters be non-type parameters of type char, while the last of them
may be a parameter pack.

I'm not yet used to user-defined literals, but ... Why do you define
{{ operatorl "" b() }} and not {{ operator "" b () }} ?

A research in the last working draft freely available didn't get anything.

Thanks in advance,
Leo

 

[Alf P. Steinbach /Usenet]

* Leo Equinox Gaspard, on 07.07.2011 11:58:

Le 06/07/2011 17:53, Inconnu a écrit :

I'm not yet used to user-defined literals, but ... Why do you define
{{ operatorl "" b() }} and not {{ operator "" b () }} ?

A research in the last working draft freely available didn't get anything.

Thanks in advance,
Leo

This is very ugly.

Who is the person that introduced this stuff and that should now be killed?


- Alf