Template function argument deduction with enable_if - reference to pointer
1
Maybe there is good solution that work on g++ 4.6.{3,4} ?
You can check in on https://godbolt.org/
#include <type_traits>
class A{};
class B{};
class C{
public:
A* a;
B* b;
};
template<typename T, typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type* = nullptr >
void f(T&& t) {
return;
}
int main() {
C c;
auto& cRef = c;
f(cRef.a);
f(c.a);
}
g++ /tmp/enable_if.cpp -std=c++0x
/tmp/enable_if.cpp: In function ‘int main()’:
/tmp/enable_if.cpp:20:13: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:20:13: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
/tmp/enable_if.cpp:21:10: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:21:10: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
c++ c++11 c++03
edited Nov 14 '18 at 13:08
Oktalist
10k12848
asked Nov 14 '18 at 11:52
RomaRoma
184
add a comment |
1
Maybe there is good solution that work on g++ 4.6.{3,4} ?
You can check in on https://godbolt.org/
#include <type_traits>
class A{};
class B{};
class C{
public:
A* a;
B* b;
};
template<typename T, typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type* = nullptr >
void f(T&& t) {
return;
}
int main() {
C c;
auto& cRef = c;
f(cRef.a);
f(c.a);
}
g++ /tmp/enable_if.cpp -std=c++0x
/tmp/enable_if.cpp: In function ‘int main()’:
/tmp/enable_if.cpp:20:13: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:20:13: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
/tmp/enable_if.cpp:21:10: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:21:10: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
c++ c++11 c++03
edited Nov 14 '18 at 13:08
Oktalist
10k12848
asked Nov 14 '18 at 11:52
RomaRoma
184
Please keep the title as a short summary of the problem you have, not as a piece of crucial information (like showing error messages etc.). If you have a build error, then copy-paste (as text) the full and complete output into the question body.
– Some programmer dude
Nov 14 '18 at 11:57
thnx for your comments, fixed :)
– Roma
Nov 14 '18 at 12:06
add a comment |
1
1
1
0
Maybe there is good solution that work on g++ 4.6.{3,4} ?
You can check in on https://godbolt.org/
#include <type_traits>
class A{};
class B{};
class C{
public:
A* a;
B* b;
};
template<typename T, typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type* = nullptr >
void f(T&& t) {
return;
}
int main() {
C c;
auto& cRef = c;
f(cRef.a);
f(c.a);
}
g++ /tmp/enable_if.cpp -std=c++0x
/tmp/enable_if.cpp: In function ‘int main()’:
/tmp/enable_if.cpp:20:13: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:20:13: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
/tmp/enable_if.cpp:21:10: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:21:10: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
c++ c++11 c++03
edited Nov 14 '18 at 13:08
Oktalist
10k12848
asked Nov 14 '18 at 11:52
RomaRoma
184
Maybe there is good solution that work on g++ 4.6.{3,4} ?
You can check in on https://godbolt.org/
#include <type_traits>
class A{};
class B{};
class C{
public:
A* a;
B* b;
};
template<typename T, typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type* = nullptr >
void f(T&& t) {
return;
}
int main() {
C c;
auto& cRef = c;
f(cRef.a);
f(c.a);
}
g++ /tmp/enable_if.cpp -std=c++0x
/tmp/enable_if.cpp: In function ‘int main()’:
/tmp/enable_if.cpp:20:13: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:20:13: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
/tmp/enable_if.cpp:21:10: error: no matching function for call to ‘f(A*&)’
/tmp/enable_if.cpp:21:10: note: candidate is:
/tmp/enable_if.cpp:13:6: note: template<class T, typename std::enable_if<std::is_same<typename std::remove_reference<_MemPtr>::type, A*>::value, void>::type* <anonymous> > void f(T&&)
c++ c++11 c++03
c++ c++11 c++03
edited Nov 14 '18 at 13:08
Oktalist
10k12848
asked Nov 14 '18 at 11:52
RomaRoma
184
edited Nov 14 '18 at 13:08
Oktalist
10k12848
asked Nov 14 '18 at 11:52
RomaRoma
184
edited Nov 14 '18 at 13:08
Oktalist
10k12848
edited Nov 14 '18 at 13:08
Oktalist
10k12848
edited Nov 14 '18 at 13:08
Oktalist
10k12848
10k12848
asked Nov 14 '18 at 11:52
RomaRoma
184
asked Nov 14 '18 at 11:52
RomaRoma
184
asked Nov 14 '18 at 11:52
RomaRoma
184
184
Please keep the title as a short summary of the problem you have, not as a piece of crucial information (like showing error messages etc.). If you have a build error, then copy-paste (as text) the full and complete output into the question body.
– Some programmer dude
Nov 14 '18 at 11:57
thnx for your comments, fixed :)
– Roma
Nov 14 '18 at 12:06
add a comment |
Please keep the title as a short summary of the problem you have, not as a piece of crucial information (like showing error messages etc.). If you have a build error, then copy-paste (as text) the full and complete output into the question body.
– Some programmer dude
Nov 14 '18 at 11:57
thnx for your comments, fixed :)
– Roma
Nov 14 '18 at 12:06
Please keep the title as a short summary of the problem you have, not as a piece of crucial information (like showing error messages etc.). If you have a build error, then copy-paste (as text) the full and complete output into the question body.
– Some programmer dude
Nov 14 '18 at 11:57
Please keep the title as a short summary of the problem you have, not as a piece of crucial information (like showing error messages etc.). If you have a build error, then copy-paste (as text) the full and complete output into the question body.
– Some programmer dude
Nov 14 '18 at 11:57
thnx for your comments, fixed :)
– Roma
Nov 14 '18 at 12:06
thnx for your comments, fixed :)
– Roma
Nov 14 '18 at 12:06
add a comment |
1 Answer
1
active
oldest
votes
6
The feature that allows you to default a function template parameter was introduced in C++11. Your compiler actually does not have a full support for this feature. As a workaround, you can put std::enable_if as a function return type:
template<typename T >
typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type f(T&& t) {
return;
}
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
4
@Roma - You can specify a second argument toenable_if, that it should expose as::type. So you can put it in the return type even if you need to returnbool.
– StoryTeller
Nov 14 '18 at 13:32
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
6
The feature that allows you to default a function template parameter was introduced in C++11. Your compiler actually does not have a full support for this feature. As a workaround, you can put std::enable_if as a function return type:
template<typename T >
typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type f(T&& t) {
return;
}
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
4
@Roma - You can specify a second argument toenable_if, that it should expose as::type. So you can put it in the return type even if you need to returnbool.
– StoryTeller
Nov 14 '18 at 13:32
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
add a comment |
6
The feature that allows you to default a function template parameter was introduced in C++11. Your compiler actually does not have a full support for this feature. As a workaround, you can put std::enable_if as a function return type:
template<typename T >
typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type f(T&& t) {
return;
}
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
4
@Roma - You can specify a second argument toenable_if, that it should expose as::type. So you can put it in the return type even if you need to returnbool.
– StoryTeller
Nov 14 '18 at 13:32
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
add a comment |
6
6
6
The feature that allows you to default a function template parameter was introduced in C++11. Your compiler actually does not have a full support for this feature. As a workaround, you can put std::enable_if as a function return type:
template<typename T >
typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type f(T&& t) {
return;
}
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
The feature that allows you to default a function template parameter was introduced in C++11. Your compiler actually does not have a full support for this feature. As a workaround, you can put std::enable_if as a function return type:
template<typename T >
typename std::enable_if<std::is_same<typename std::remove_reference<T>::type,A*>::value>::type f(T&& t) {
return;
}
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
answered Nov 14 '18 at 13:03
Rafał GórczewskiRafał Górczewski
1517
1517
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
4
@Roma - You can specify a second argument toenable_if, that it should expose as::type. So you can put it in the return type even if you need to returnbool.
– StoryTeller
Nov 14 '18 at 13:32
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
add a comment |
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
4
@Roma - You can specify a second argument toenable_if, that it should expose as::type. So you can put it in the return type even if you need to returnbool.
– StoryTeller
Nov 14 '18 at 13:32
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
thnx, out actual function return type is bool, but putting enable_if in function arguments also work.
– Roma
Nov 14 '18 at 13:15
4
4
@Roma - You can specify a second argument to
enable_if, that it should expose as ::type. So you can put it in the return type even if you need to return bool.– StoryTeller
Nov 14 '18 at 13:32
@Roma - You can specify a second argument to
enable_if, that it should expose as ::type. So you can put it in the return type even if you need to return bool.– StoryTeller
Nov 14 '18 at 13:32
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
@StoryTeller , o, thnx !!! good to know :)
– Roma
Nov 14 '18 at 13:41
add a comment |
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Please keep the title as a short summary of the problem you have, not as a piece of crucial information (like showing error messages etc.). If you have a build error, then copy-paste (as text) the full and complete output into the question body.
– Some programmer dude
Nov 14 '18 at 11:57
thnx for your comments, fixed :)
– Roma
Nov 14 '18 at 12:06