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My Integral concept
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porp...@gmail.com
Sep 15, 2019, 5:51:15 AM9/15/19
to
Hi,
I've defined the following concept.
But the compiler does not report constraint error with non-integral "Car" type.
Is my concept correct ?
If not, could you please write what should I do to make it correct.
I'm using gcc 7.4.0.
Thank you
template < typename T >
concept bool Integral = requires ( T t ) {
{ std::is_integral<T>::value } -> bool;
};
template < Integral T >
void fun ( T t )
{
}
struct Car {};
int main ()
{
Car c;
fun ( c );
return 0;
}
I've defined the following concept.
But the compiler does not report constraint error with non-integral "Car" type.
Is my concept correct ?
If not, could you please write what should I do to make it correct.
I'm using gcc 7.4.0.
Thank you
template < typename T >
concept bool Integral = requires ( T t ) {
{ std::is_integral<T>::value } -> bool;
};
template < Integral T >
void fun ( T t )
{
}
struct Car {};
int main ()
{
Car c;
fun ( c );
return 0;
}
Juha Nieminen
Sep 15, 2019, 6:39:41 AM9/15/19
to
Öö Tiib
Sep 15, 2019, 7:05:06 AM9/15/19
to
Demo: http://coliru.stacked-crooked.com/a/5e968a4ed8bd8c08
Öö Tiib
Sep 15, 2019, 7:22:24 AM9/15/19
to
On Sunday, 15 September 2019 12:51:15 UTC+3, porp...@gmail.com wrote:
>
> template < typename T >
> concept bool Integral = requires ( T t ) {
> { std::is_integral<T>::value } -> bool;
> };
I guess you wanted to write here:
>
> template < typename T >
> concept bool Integral = requires ( T t ) {
> { std::is_integral<T>::value } -> bool;
> };
template < typename T >
concept Integral = std::is_integral<T>::value;
Bo Persson
Sep 15, 2019, 7:30:46 AM9/15/19
to
The problem with the first concept attempt is that
is_integral<Car>::value is still a bool, only with value false.
Bo Persson
porp...@gmail.com
Sep 21, 2019, 6:43:43 AM9/21/19
to
Could you please give me some rules of when to use short form of a concept, like:
template < typename T >
concept Integral = std::is_integral<T>::value;
and when to use a longer one, like:
concept Integral = std::is_integral<T>::value;
template < typename T >
concept bool Integral = requires ( T t ) {
{ std::is_integral<T>::value } -> bool;
};
I mean I have only 2 examples above and found others on the internet but I don't get the general rule.
concept bool Integral = requires ( T t ) {
{ std::is_integral<T>::value } -> bool;
};
Bo Persson
Sep 21, 2019, 8:34:38 AM9/21/19
to
TS (ISO Technical Specification), while the shorter form looks like what
made into the (still draft) C++20 language.
https://en.cppreference.com/w/cpp/experimental/constraints
https://en.cppreference.com/w/cpp/language/constraints
Then there is the problem of which version, if any, your compiler is
supposed to support. :-)
Bo Persson
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