I have a custom class, Coord (stands for Coordinates). When I try to create a constructor of Coord with its x and y variables, it works fine. However, when I try to store a the Coord in an unordered_map, it fails.
Coord Class
class Coord{
public:
int x, y;
public:
Coord(int x1, int y1) {
x = x1;
y = y1;
}
int getX(void) const{
return x;
}
int getY(void) const{
return y;
}
bool operator<(const Coord& other) const
{ return x<other.x || (!(x<other.x) && y<other.y); }
bool operator==(const Coord &other) const
{
return (x == other.x && y == other.y);
}
};
I have no problem initialising a Coord object with x and y values
Coord start = Coord(0,0);
I created a unordered_map object, and tried to insert Coord objects into it. The code below works.
unordered_map<Coord, Coord> came_from;
Coord start = Coord(0,0);
came_from.insert({start, start});
Then I tried to subscript. This gave me a no matching constructor for initialisation of 'Coord'
unordered_map<Coord, Coord> came_from;
Coord start = Coord(0,0);
came_from[start] = start;
Full Error Message
error: no matching constructor for
initialization of 'Coord'
second(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/utility:487:11: note: in instantiation of function template
specialization 'std::__1::pair<const Coord, Coord>::pair<const Coord &, 0>' requested here
: pair(__pc, __first_args, __second_args,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory:1805:31: note: in instantiation of function template
specialization 'std::__1::pair<const Coord, Coord>::pair<const Coord &>' requested here
::new((void*)__p) _Up(_VSTD::forward<_Args>(__args)...);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory:1715:18: note: in instantiation of function template
specialization 'std::__1::allocator<std::__1::__hash_node<std::__1::__hash_value_type<Coord, Coord>, void *> >::construct<std::__1::pair<const Coord,
Coord>, const std::__1::piecewise_construct_t &, std::__1::tuple<const Coord &>, std::__1::tuple<> >' requested here
{__a.construct(__p, _VSTD::forward<_Args>(__args)...);}
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory:1561:14: note: in instantiation of function template
specialization 'std::__1::allocator_traits<std::__1::allocator<std::__1::__hash_node<std::__1::__hash_value_type<Coord, Coord>, void *> >
>::__construct<std::__1::pair<const Coord, Coord>, const std::__1::piecewise_construct_t &, std::__1::tuple<const Coord &>, std::__1::tuple<> >'
requested here
{__construct(__has_construct<allocator_type, _Tp*, _Args...>(),
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__hash_table:2305:20: note: in instantiation of function
template specialization 'std::__1::allocator_traits<std::__1::allocator<std::__1::__hash_node<std::__1::__hash_value_type<Coord, Coord>, void *> >
>::construct<std::__1::pair<const Coord, Coord>, const std::__1::piecewise_construct_t &, std::__1::tuple<const Coord &>, std::__1::tuple<> >' requested
here
__node_traits::construct(__na, _NodeTypes::__get_ptr(__h->__value_),
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__hash_table:2021:29: note: in instantiation of function
template specialization 'std::__1::__hash_table<std::__1::__hash_value_type<Coord, Coord>, std::__1::__unordered_map_hasher<Coord,
std::__1::__hash_value_type<Coord, Coord>, std::__1::hash<Coord>, true>, std::__1::__unordered_map_equal<Coord, std::__1::__hash_value_type<Coord,
Coord>, std::__1::equal_to<Coord>, true>, std::__1::allocator<std::__1::__hash_value_type<Coord, Coord> > >::__construct_node_hash<const
std::__1::piecewise_construct_t &, std::__1::tuple<const Coord &>, std::__1::tuple<> >' requested here
__node_holder __h = __construct_node_hash(__hash, _VSTD::forward<_Args>(__args)...);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/unordered_map:1386:21: note: in instantiation of function
template specialization 'std::__1::__hash_table<std::__1::__hash_value_type<Coord, Coord>, std::__1::__unordered_map_hasher<Coord,
std::__1::__hash_value_type<Coord, Coord>, std::__1::hash<Coord>, true>, std::__1::__unordered_map_equal<Coord, std::__1::__hash_value_type<Coord,
Coord>, std::__1::equal_to<Coord>, true>, std::__1::allocator<std::__1::__hash_value_type<Coord, Coord> > >::__emplace_unique_key_args<Coord, const
std::__1::piecewise_construct_t &, std::__1::tuple<const Coord &>, std::__1::tuple<> >' requested here
return __table_.__emplace_unique_key_args(__k,
^
lab1.cpp:341:14: note: in instantiation of member function 'std::__1::unordered_map<Coord, Coord, std::__1::hash<Coord>, std::__1::equal_to<Coord>,
std::__1::allocator<std::__1::pair<const Coord, Coord> > >::operator[]' requested here
came_from[start] = start;
^
lab1.cpp:34:7: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 0 were provided
class Coord{
^
lab1.cpp:34:7: note: candidate constructor (the implicit move constructor) not viable: requires 1 argument, but 0 were provided
lab1.cpp:39:9: note: candidate constructor not viable: requires 2 arguments, but 0 were provided
Coord(int x1, int y1) {
I have looked at the duplicated link you showed me, but I am not sure how it solves this problem. Can you please help? Cause it hashes perfectly fine
