C++ c++；引用是否在需要时隐式转换为值？
我有以下代码：C++ c++；引用是否在需要时隐式转换为值？,c++,reference,C++,Reference,我有以下代码： #include <stdio.h> #include <math.h> #include <array> #include <unordered_set> using namespace std; class Circle { public: int x; int y; int r; Circle() : x(0), y(0), r(0) {} Circle(int x, int
#include <stdio.h>
#include <math.h>
#include <array>
#include <unordered_set>
using namespace std;
class Circle {
public:
int x;
int y;
int r;
Circle() : x(0), y(0), r(0) {}
Circle(int x, int y, int r) {
this->x = x;
this->y = y;
this->r = r;
}
double area() {
return PI * pow(r, 2);
}
};
vector <Circle> filter_circles(vector <Circle> &circles) {
auto stringify = [](const pair<int, int> &p, string sep = "-") -> string {
return to_string(p.first) + sep + to_string(p.second);
};
unordered_set <string> circles_seen;
vector <Circle> distinct;
for (auto &c: circles) {
auto centre = stringify(make_pair(c.x, c.y));
if (circles_seen.find(centre) == circles_seen.end()) {
distinct.push_back(c);
} else {
circles_seen.insert(centre);
}
}
return distinct;
}
Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1785:16: error: 'pointer' declared as a pointer to a reference of type 'Circle &'
typedef _Tp* pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1514:22: note: in instantiation of template class 'std::__1::allocator<Circle &>' requested here
typedef typename allocator_type::value_type value_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
In file included from dartboard_detector.cpp:2:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv/cv.h:64:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:53:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/algorithm:644:
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1786:22: error: 'const_pointer' declared as a pointer to a reference of type 'Circle &'
typedef const _Tp* const_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1805:45: error: multiple overloads of 'address' instantiate to the same signature 'std::__1::allocator<Circle &>::const_pointer
(std::__1::allocator<Circle &>::const_reference) const noexcept' (aka 'int (Circle &) const noexcept')
_LIBCPP_INLINE_VISIBILITY const_pointer address(const_reference __x) const _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1803:39: note: previous declaration is here
_LIBCPP_INLINE_VISIBILITY pointer address(reference __x) const _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:951:22: error: implicit instantiation of undefined template 'std::__1::__pointer_traits_element_type<int, false>'
typedef typename __pointer_traits_element_type<pointer>::type element_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1073:22: note: in instantiation of template class 'std::__1::pointer_traits<int>' requested here
typedef typename pointer_traits<_Ptr>::template rebind<void> type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1518:22: note: in instantiation of template class 'std::__1::__void_pointer<int, std::__1::allocator<Circle &>, false>' requested here
typedef typename __void_pointer<pointer, allocator_type>::type void_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:741:8: note: template is declared here
struct __pointer_traits_element_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1073:53: error: no member named 'rebind' in 'std::__1::pointer_traits<int>'
typedef typename pointer_traits<_Ptr>::template rebind<void> type;
~~~~~~~~~~~~~~~~~~~~~~ ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1518:22: note: in instantiation of template class 'std::__1::__void_pointer<int, std::__1::allocator<Circle &>, false>' requested here
typedef typename __void_pointer<pointer, allocator_type>::type void_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
In file included from dartboard_detector.cpp:2:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv/cv.h:64:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:53:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/algorithm:644:
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:851:22: error: type 'int' cannot be used prior to '::' because it has no members
typedef typename _Tp::template rebind<_Up> type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:955:26: note: in instantiation of template class 'std::__1::__pointer_traits_rebind<int, const void, false>' requested here
template <class _Up> using rebind = typename __pointer_traits_rebind<pointer, _Up>::type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1096:53: note: in instantiation of template type alias 'rebind' requested here
typedef typename pointer_traits<_Ptr>::template rebind<const void> type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1519:22: note: in instantiation of template class 'std::__1::__const_void_pointer<int, std::__1::allocator<Circle &>, false>' requested here
typedef typename __const_void_pointer<pointer, allocator_type>::type const_void_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
In file included from dartboard_detector.cpp:2:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv/cv.h:64:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:60:
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:475:30: error: 'reference' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::reference reference;
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:329:54: note: declared protected here
typedef value_type& reference;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:476:30: error: 'const_reference' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::const_reference const_reference;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:330:54: note: declared protected here
typedef const value_type& const_reference;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:478:30: error: 'difference_type' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::difference_type difference_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:331:54: note: declared protected here
typedef typename __alloc_traits::difference_type difference_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:479:30: error: 'pointer' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::pointer pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:332:54: note: declared protected here
typedef typename __alloc_traits::pointer pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:480:30: error: 'const_pointer' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::const_pointer const_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:333:54: note: declared protected here
typedef typename __alloc_traits::const_pointer const_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:688:15: error: 'data' declared as a pointer to a reference of type 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >::value_type' (aka 'Circle &')
value_type* data() _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:691:21: error: 'data' declared as a pointer to a reference of type 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >::value_type' (aka 'Circle &')
const value_type* data() const _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:708:36: error: multiple overloads of 'push_back' instantiate to the same signature 'void (Circle &)'
_LIBCPP_INLINE_VISIBILITY void push_back(value_type&& __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:705:36: note: previous declaration is here
_LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:725:14: error: multiple overloads of 'insert' instantiate to the same signature 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >::iterator
(std::__1::vector<Circle &, std::__1::allocator<Circle &> >::const_iterator, Circle &)' (aka '__wrap_iter<int> (__wrap_iter<int>, Circle &)')
iterator insert(const_iterator __position, value_type&& __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:722:14: note: previous declaration is here
iterator insert(const_iterator __position, const_reference __x);
^
dartboard_detector.cpp:72:12: error: no viable conversion from returned value of type 'vector<Circle>' to function return type 'vector<Circle &>'
return distinct;
^~~~~~~~
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:551:5: note: candidate constructor not viable: no known conversion from 'vector<Circle>' to 'const std::__1::vector<Circle &, std::__1::allocator<Circle &> > &' for 1st
argument
vector(const vector& __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:558:5: note: candidate constructor not viable: no known conversion from 'vector<Circle>' to 'initializer_list<std::__1::vector<Circle &, std::__1::allocator<Circle &>
>::value_type>' (aka 'initializer_list<Circle &>') for 1st argument
vector(initializer_list<value_type> __il);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:564:5: note: candidate constructor not viable: no known conversion from 'vector<Circle>' to 'std::__1::vector<Circle &, std::__1::allocator<Circle &> > &&' for 1st
argument
vector(vector&& __x)
^
Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1785:16:错误：“指针”声明为指向“Circle&”类型引用的指针
typedef_Tp*指针；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1514:22:注意：在这里请求的模板类“std:：u 1:：allocator”的实例化中
typedef typename分配器\类型：：值\类型值\类型；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22：注意：在模板类的实例化中，此处请求了“std:：u 1:：allocator_traits”
typedef typename\uuuu alloc\u traits:：size\u type size\u type；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15：注意：在模板类的实例化中，此处请求“std:：u 1:：u vector_base”
：private uu向量u基
^
dartboard_detector.cpp:57:18:注意：在模板类“std:：_1:：vector”的实例化中，此处请求
向量过滤器_圆（向量和圆）{
^
在dartboard_detector.cpp中包含的文件中：2：
在/usr/local/ceral中包含的文件中/opencv@2/2.4.13.7_5/include/opencv/cv.h:64：
在/usr/local/ceral中包含的文件中/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:53：
在/Library/Developer/CommandLineTools/usr/include/c++/v1/algorithm:644中包含的文件中：
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1786:22:错误：“const_pointer”声明为指向“Circle&”类型引用的指针
typedef const_Tp*const_指针；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1805:45:错误：“address”的多个重载实例化为同一签名“std:：u 1:：allocator:：const_pointer”
（std:：_1:：分配器：：常量引用）常量noexcept'（也称为“int（Circle&）const noexcept'）
_LIBCPP_INLINE_可见性常量指针地址（常量引用x）常量NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1803:39：注意：前面的声明在这里
_LIBCPP_INLINE_可见性指针地址（reference _x）const NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:951:22:错误：未定义模板的隐式实例化“std:：\uuu 1:：\uu指针\u特征\u元素\u类型”
typedef typename\uuuu指针\utraits\uelement\utype:：type element\utype；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1073:22：注意：在模板类的实例化中，此处请求了“std:：u 1:：pointer_traits”
typedef typename指针_traits:：模板重新绑定类型；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1518:22：注意：在模板类的实例化中，此处请求了“std:：\uu 1:：\uu void\u pointer”
typedef typename\uu void\u指针：：type void\u指针；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22：注意：在模板类的实例化中，此处请求了“std:：u 1:：allocator_traits”
typedef typename\uuuu alloc\u traits:：size\u type size\u type；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15：注意：在模板类的实例化中，此处请求“std:：u 1:：u vector_base”
：private uu向量u基
^
dartboard_detector.cpp:57:18:注意：在模板类“std:：_1:：vector”的实例化中，此处请求
向量过滤器_圆（向量和圆）{
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:741:8：注意：这里声明了模板
结构\指针\特征\元素\类型；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1073:53:错误：在“std:：\uu 1:：pointer\u traits”中没有名为“rebind”的成员
typedef typename指针_traits:：模板重新绑定类型；
~~~~~~~~~~~~~~~~~~~~~~ ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1518:22：注意：在模板类的实例化中，此处请求了“std:：\uu 1:：\uu void\u pointer”
typedef typename\uu void\u指针：：type void\u指针；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22：注意：在模板类的实例化中，此处请求了“std:：u 1:：allocator_traits”
typedef typename\uuuu alloc\u traits:：size\u type size\u type；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15：注意：在模板类的实例化中，此处请求“std:：u 1:：u vector_base”
：private uu向量u基
^
dartboard_detector.cpp:57:18:注意：在模板类“std:：_1:：vector”的实例化中，此处请求
向量过滤器_圆（向量和圆）{
^
在dartboard_detector.cpp中包含的文件中：2：
在/usr/local/ceral中包含的文件中/opencv@2/2.4.13.7_5/include/opencv/cv.h:64：
在/usr/local/ceral中包含的文件中/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:53：
在/Library/Developer/CommandLineTools/usr/include/c++/v1/algorithm:644中包含的文件中：
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:851:22:错误：类型“int”不能在“：”之前使用，因为它没有成员
typedef typename _Tp:：模板重新绑定类型；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:955:26:注意：在模板类的实例化中，此处请求了“std:：\uu 1:：\uu指针\u特征\u重新绑定”
模板使用rebind=typename\uuuu pointer\utraits\urebind:：type；
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1096:53:注意：在模板类型的实例化中，此处请求别名“rebind”
typedef typename指针_traits:：模板重新绑定类型；
^
/库/开发人员/命令行工具/usr/inclu
Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1785:16: error: 'pointer' declared as a pointer to a reference of type 'Circle &'
typedef _Tp* pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1514:22: note: in instantiation of template class 'std::__1::allocator<Circle &>' requested here
typedef typename allocator_type::value_type value_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
In file included from dartboard_detector.cpp:2:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv/cv.h:64:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:53:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/algorithm:644:
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1786:22: error: 'const_pointer' declared as a pointer to a reference of type 'Circle &'
typedef const _Tp* const_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1805:45: error: multiple overloads of 'address' instantiate to the same signature 'std::__1::allocator<Circle &>::const_pointer
(std::__1::allocator<Circle &>::const_reference) const noexcept' (aka 'int (Circle &) const noexcept')
_LIBCPP_INLINE_VISIBILITY const_pointer address(const_reference __x) const _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1803:39: note: previous declaration is here
_LIBCPP_INLINE_VISIBILITY pointer address(reference __x) const _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:951:22: error: implicit instantiation of undefined template 'std::__1::__pointer_traits_element_type<int, false>'
typedef typename __pointer_traits_element_type<pointer>::type element_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1073:22: note: in instantiation of template class 'std::__1::pointer_traits<int>' requested here
typedef typename pointer_traits<_Ptr>::template rebind<void> type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1518:22: note: in instantiation of template class 'std::__1::__void_pointer<int, std::__1::allocator<Circle &>, false>' requested here
typedef typename __void_pointer<pointer, allocator_type>::type void_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:741:8: note: template is declared here
struct __pointer_traits_element_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1073:53: error: no member named 'rebind' in 'std::__1::pointer_traits<int>'
typedef typename pointer_traits<_Ptr>::template rebind<void> type;
~~~~~~~~~~~~~~~~~~~~~~ ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1518:22: note: in instantiation of template class 'std::__1::__void_pointer<int, std::__1::allocator<Circle &>, false>' requested here
typedef typename __void_pointer<pointer, allocator_type>::type void_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
In file included from dartboard_detector.cpp:2:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv/cv.h:64:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:53:
In file included from /Library/Developer/CommandLineTools/usr/include/c++/v1/algorithm:644:
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:851:22: error: type 'int' cannot be used prior to '::' because it has no members
typedef typename _Tp::template rebind<_Up> type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:955:26: note: in instantiation of template class 'std::__1::__pointer_traits_rebind<int, const void, false>' requested here
template <class _Up> using rebind = typename __pointer_traits_rebind<pointer, _Up>::type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1096:53: note: in instantiation of template type alias 'rebind' requested here
typedef typename pointer_traits<_Ptr>::template rebind<const void> type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:1519:22: note: in instantiation of template class 'std::__1::__const_void_pointer<int, std::__1::allocator<Circle &>, false>' requested here
typedef typename __const_void_pointer<pointer, allocator_type>::type const_void_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:326:22: note: in instantiation of template class 'std::__1::allocator_traits<std::__1::allocator<Circle &> >' requested here
typedef typename __alloc_traits::size_type size_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:465:15: note: in instantiation of template class 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >' requested here
: private __vector_base<_Tp, _Allocator>
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
In file included from dartboard_detector.cpp:2:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv/cv.h:64:
In file included from /usr/local/Cellar/opencv@2/2.4.13.7_5/include/opencv2/core/core.hpp:60:
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:475:30: error: 'reference' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::reference reference;
^
dartboard_detector.cpp:57:18: note: in instantiation of template class 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >' requested here
vector <Circle&> filter_circles(vector <Circle> &circles) {
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:329:54: note: declared protected here
typedef value_type& reference;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:476:30: error: 'const_reference' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::const_reference const_reference;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:330:54: note: declared protected here
typedef const value_type& const_reference;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:478:30: error: 'difference_type' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::difference_type difference_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:331:54: note: declared protected here
typedef typename __alloc_traits::difference_type difference_type;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:479:30: error: 'pointer' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::pointer pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:332:54: note: declared protected here
typedef typename __alloc_traits::pointer pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:480:30: error: 'const_pointer' is a protected member of 'std::__1::__vector_base<Circle &, std::__1::allocator<Circle &> >'
typedef typename __base::const_pointer const_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:333:54: note: declared protected here
typedef typename __alloc_traits::const_pointer const_pointer;
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:688:15: error: 'data' declared as a pointer to a reference of type 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >::value_type' (aka 'Circle &')
value_type* data() _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:691:21: error: 'data' declared as a pointer to a reference of type 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >::value_type' (aka 'Circle &')
const value_type* data() const _NOEXCEPT
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:708:36: error: multiple overloads of 'push_back' instantiate to the same signature 'void (Circle &)'
_LIBCPP_INLINE_VISIBILITY void push_back(value_type&& __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:705:36: note: previous declaration is here
_LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:725:14: error: multiple overloads of 'insert' instantiate to the same signature 'std::__1::vector<Circle &, std::__1::allocator<Circle &> >::iterator
(std::__1::vector<Circle &, std::__1::allocator<Circle &> >::const_iterator, Circle &)' (aka '__wrap_iter<int> (__wrap_iter<int>, Circle &)')
iterator insert(const_iterator __position, value_type&& __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:722:14: note: previous declaration is here
iterator insert(const_iterator __position, const_reference __x);
^
dartboard_detector.cpp:72:12: error: no viable conversion from returned value of type 'vector<Circle>' to function return type 'vector<Circle &>'
return distinct;
^~~~~~~~
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:551:5: note: candidate constructor not viable: no known conversion from 'vector<Circle>' to 'const std::__1::vector<Circle &, std::__1::allocator<Circle &> > &' for 1st
argument
vector(const vector& __x);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:558:5: note: candidate constructor not viable: no known conversion from 'vector<Circle>' to 'initializer_list<std::__1::vector<Circle &, std::__1::allocator<Circle &>
>::value_type>' (aka 'initializer_list<Circle &>') for 1st argument
vector(initializer_list<value_type> __il);
^
/Library/Developer/CommandLineTools/usr/include/c++/v1/vector:564:5: note: candidate constructor not viable: no known conversion from 'vector<Circle>' to 'std::__1::vector<Circle &, std::__1::allocator<Circle &> > &&' for 1st
argument
vector(vector&& __x)
^
vector <Circle> distinct;
for (auto &c: circles) {
auto centre = stringify(make_pair(c.x, c.y));
if (circles_seen.find(centre) == circles_seen.end()) {
distinct.push_back(c);
} else {
circles_seen.insert(centre);
}
}
void push_back(const Circle& value);
void f(int a);
void g(int& b);
int c = 42;
int& d = c;
f(c);
f(d);
g(c);
g(d);