How do I use concepts in if-constexpr?
How does one use concepts in if constexpr?
Given the example below, what would one give to if constexpr to return 1 in case T meets the requirements of integral and else 0?
template<typename T>
concept integral = std::is_integral_v<T>;
struct X{};
template<typename T>
constexpr auto a () {
if constexpr (/* T is integral */) {
return 1;
}
else {
return 0;
}
}
int main () {
return a<X>();
}
c++ c++-concepts c++20 if-constexpr
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
add a comment |
How does one use concepts in if constexpr?
Given the example below, what would one give to if constexpr to return 1 in case T meets the requirements of integral and else 0?
template<typename T>
concept integral = std::is_integral_v<T>;
struct X{};
template<typename T>
constexpr auto a () {
if constexpr (/* T is integral */) {
return 1;
}
else {
return 0;
}
}
int main () {
return a<X>();
}
c++ c++-concepts c++20 if-constexpr
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
add a comment |
How does one use concepts in if constexpr?
Given the example below, what would one give to if constexpr to return 1 in case T meets the requirements of integral and else 0?
template<typename T>
concept integral = std::is_integral_v<T>;
struct X{};
template<typename T>
constexpr auto a () {
if constexpr (/* T is integral */) {
return 1;
}
else {
return 0;
}
}
int main () {
return a<X>();
}
c++ c++-concepts c++20 if-constexpr
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
How does one use concepts in if constexpr?
Given the example below, what would one give to if constexpr to return 1 in case T meets the requirements of integral and else 0?
template<typename T>
concept integral = std::is_integral_v<T>;
struct X{};
template<typename T>
constexpr auto a () {
if constexpr (/* T is integral */) {
return 1;
}
else {
return 0;
}
}
int main () {
return a<X>();
}
c++ c++-concepts c++20 if-constexpr
c++ c++-concepts c++20 if-constexpr
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
edited Feb 11 at 13:37
Peter Mortensen
13.6k1986111
13.6k1986111
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
asked Feb 7 at 12:32
kawillzockenkawillzocken
480315
480315
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
Concepts are named boolean predicates on template parameters, evaluated at compile time.
In a constexpr if statement, the value of the condition must be a contextually converted constant expression of type bool.
So in this case, usage is simple:
if constexpr ( integral<T> )
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
answered Feb 7 at 13:10
P.WP.W
14.1k31248
add a comment |
It is sufficient to do:
if constexpr ( integral<T> )
edited Feb 7 at 14:52
Barry
182k20316580
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Concepts are named boolean predicates on template parameters, evaluated at compile time.
In a constexpr if statement, the value of the condition must be a contextually converted constant expression of type bool.
So in this case, usage is simple:
if constexpr ( integral<T> )
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
answered Feb 7 at 13:10
P.WP.W
14.1k31248
add a comment |
Concepts are named boolean predicates on template parameters, evaluated at compile time.
In a constexpr if statement, the value of the condition must be a contextually converted constant expression of type bool.
So in this case, usage is simple:
if constexpr ( integral<T> )
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
answered Feb 7 at 13:10
P.WP.W
14.1k31248
add a comment |
Concepts are named boolean predicates on template parameters, evaluated at compile time.
In a constexpr if statement, the value of the condition must be a contextually converted constant expression of type bool.
So in this case, usage is simple:
if constexpr ( integral<T> )
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
answered Feb 7 at 13:10
P.WP.W
14.1k31248
Concepts are named boolean predicates on template parameters, evaluated at compile time.
In a constexpr if statement, the value of the condition must be a contextually converted constant expression of type bool.
So in this case, usage is simple:
if constexpr ( integral<T> )
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
answered Feb 7 at 13:10
P.WP.W
14.1k31248
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
edited Feb 11 at 13:38
Peter Mortensen
13.6k1986111
13.6k1986111
answered Feb 7 at 13:10
P.WP.W
14.1k31248
answered Feb 7 at 13:10
P.WP.W
14.1k31248
answered Feb 7 at 13:10
P.WP.W
14.1k31248
14.1k31248
add a comment |
add a comment |
It is sufficient to do:
if constexpr ( integral<T> )
edited Feb 7 at 14:52
Barry
182k20316580
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
add a comment |
It is sufficient to do:
if constexpr ( integral<T> )
edited Feb 7 at 14:52
Barry
182k20316580
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
add a comment |
It is sufficient to do:
if constexpr ( integral<T> )
edited Feb 7 at 14:52
Barry
182k20316580
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
It is sufficient to do:
if constexpr ( integral<T> )
edited Feb 7 at 14:52
Barry
182k20316580
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
edited Feb 7 at 14:52
Barry
182k20316580
edited Feb 7 at 14:52
Barry
182k20316580
edited Feb 7 at 14:52
Barry
182k20316580
182k20316580
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
answered Feb 7 at 12:36
kawillzockenkawillzocken
480315
480315
add a comment |
add a comment |
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