Unable to create unordered_set with lambda function

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up vote
6
down vote

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I get the error

error: call to implicitly-deleted default constructor of '__compressed_pair_elem<(lambda at 
main.cpp:181:16), 1>': _Base1(std::forward<_Tp>(__t)), _Base2() 

with the following code. What's the mistake I am making and I couldn't understand the error as well.

using namespace std;

auto my_hash = (vector<int> const& vec)
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;
;

using MySet = unordered_set<vector<int>, decltype(my_hash)>;

int main() 
 vector<int> a1,2,3;
 MySet s;
 return 0;

c++ c++11 c++14

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asked 26 mins ago

user3285099

627

add a comment | 

up vote
6
down vote

favorite

1

I get the error

error: call to implicitly-deleted default constructor of '__compressed_pair_elem<(lambda at 
main.cpp:181:16), 1>': _Base1(std::forward<_Tp>(__t)), _Base2() 

with the following code. What's the mistake I am making and I couldn't understand the error as well.

using namespace std;

auto my_hash = (vector<int> const& vec)
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;
;

using MySet = unordered_set<vector<int>, decltype(my_hash)>;

int main() 
 vector<int> a1,2,3;
 MySet s;
 return 0;

c++ c++11 c++14

share|improve this question

asked 26 mins ago

user3285099

627

add a comment | 

up vote
6
down vote

favorite

1

up vote
6
down vote

favorite

1

1

I get the error

error: call to implicitly-deleted default constructor of '__compressed_pair_elem<(lambda at 
main.cpp:181:16), 1>': _Base1(std::forward<_Tp>(__t)), _Base2() 

with the following code. What's the mistake I am making and I couldn't understand the error as well.

using namespace std;

auto my_hash = (vector<int> const& vec)
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;
;

using MySet = unordered_set<vector<int>, decltype(my_hash)>;

int main() 
 vector<int> a1,2,3;
 MySet s;
 return 0;

c++ c++11 c++14

share|improve this question

asked 26 mins ago

user3285099

627

I get the error

error: call to implicitly-deleted default constructor of '__compressed_pair_elem<(lambda at 
main.cpp:181:16), 1>': _Base1(std::forward<_Tp>(__t)), _Base2() 

with the following code. What's the mistake I am making and I couldn't understand the error as well.

using namespace std;

auto my_hash = (vector<int> const& vec)
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;
;

using MySet = unordered_set<vector<int>, decltype(my_hash)>;

int main() 
 vector<int> a1,2,3;
 MySet s;
 return 0;

c++ c++11 c++14

c++ c++11 c++14

share|improve this question

asked 26 mins ago

user3285099

627

share|improve this question

asked 26 mins ago

user3285099

627

share|improve this question

share|improve this question

asked 26 mins ago

user3285099

627

asked 26 mins ago

user3285099

627

asked 26 mins ago

user3285099

627

627

add a comment | 

add a comment | 

1 Answer
1

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oldest

votes

up vote
10
down vote

Closure types are not default-constructible prior to C++20 (see P0624). You need to pass in an instance of your hasher:

constexpr std::size_t bucket_count = 512;
MySet sbucket_count, my_hash;

live example on wandbox.org

---

Alternatively, you can use a good old struct:

struct Hasher 
auto operator()(vector<int> const& vec) const 
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;

;

using MySet = unordered_set<vector<int>, Hasher>;

int main() 
 MySet s;

live example on wandbox.org

share|improve this answer

edited 21 mins ago

answered 24 mins ago

Vittorio Romeo

54.3k16140282

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

up vote
10
down vote

Closure types are not default-constructible prior to C++20 (see P0624). You need to pass in an instance of your hasher:

constexpr std::size_t bucket_count = 512;
MySet sbucket_count, my_hash;

live example on wandbox.org

---

Alternatively, you can use a good old struct:

struct Hasher 
auto operator()(vector<int> const& vec) const 
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;

;

using MySet = unordered_set<vector<int>, Hasher>;

int main() 
 MySet s;

live example on wandbox.org

share|improve this answer

edited 21 mins ago

answered 24 mins ago

Vittorio Romeo

54.3k16140282

add a comment | 

up vote
10
down vote

Closure types are not default-constructible prior to C++20 (see P0624). You need to pass in an instance of your hasher:

constexpr std::size_t bucket_count = 512;
MySet sbucket_count, my_hash;

live example on wandbox.org

---

Alternatively, you can use a good old struct:

struct Hasher 
auto operator()(vector<int> const& vec) const 
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;

;

using MySet = unordered_set<vector<int>, Hasher>;

int main() 
 MySet s;

live example on wandbox.org

share|improve this answer

edited 21 mins ago

answered 24 mins ago

Vittorio Romeo

54.3k16140282

add a comment | 

up vote
10
down vote

up vote
10
down vote

Closure types are not default-constructible prior to C++20 (see P0624). You need to pass in an instance of your hasher:

constexpr std::size_t bucket_count = 512;
MySet sbucket_count, my_hash;

live example on wandbox.org

---

Alternatively, you can use a good old struct:

struct Hasher 
auto operator()(vector<int> const& vec) const 
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;

;

using MySet = unordered_set<vector<int>, Hasher>;

int main() 
 MySet s;

live example on wandbox.org

share|improve this answer

edited 21 mins ago

answered 24 mins ago

Vittorio Romeo

54.3k16140282

Closure types are not default-constructible prior to C++20 (see P0624). You need to pass in an instance of your hasher:

constexpr std::size_t bucket_count = 512;
MySet sbucket_count, my_hash;

live example on wandbox.org

---

Alternatively, you can use a good old struct:

struct Hasher 
auto operator()(vector<int> const& vec) const 
 size_t seed = vec.size();
 for(auto& i : vec) 
 seed ^= i + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
 return seed;

;

using MySet = unordered_set<vector<int>, Hasher>;

int main() 
 MySet s;

live example on wandbox.org

share|improve this answer

edited 21 mins ago

answered 24 mins ago

Vittorio Romeo

54.3k16140282

share|improve this answer

share|improve this answer

edited 21 mins ago

edited 21 mins ago

edited 21 mins ago

answered 24 mins ago

Vittorio Romeo

54.3k16140282

answered 24 mins ago

Vittorio Romeo

54.3k16140282

answered 24 mins ago

Vittorio Romeo

54.3k16140282

54.3k16140282

add a comment | 

add a comment | 

 

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