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Adding empty element to declared container without declaring type of element
The 2019 Stack Overflow Developer Survey Results Are In
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
The Ask Question Wizard is Live!
Data science time! April 2019 and salary with experienceHow to add element to C++ array?Why can't variables be declared in a switch statement?What are POD types in C++?How do you declare an interface in C++?Meaning of 'const' last in a function declaration of a class?Pretty-print C++ STL containersHow to implement dynamic element container in C++Is it wrong if the standard container element type and std::allocator type are different?Ending lifetime of STL container without calling the destructorenum to string in modern C++11 / C++14 / C++17 and future C++20STL container holding class within declaration of that class
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When we use a complicated container in C++, like
std::vector<std::map<std::string, std::set<std::string>>> table;
The only way to add an empty map (which may represent a row or column) is to initialize a new element and push it back. For example with
table.push_back(std::map<std::string, std::set<std::string>>());
Is there any way to avoid redeclaring the type, and just adding the correct typed element?
c++ c++11
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
asked Mar 25 at 6:35
VineetVineet
359411
add a comment |
When we use a complicated container in C++, like
std::vector<std::map<std::string, std::set<std::string>>> table;
The only way to add an empty map (which may represent a row or column) is to initialize a new element and push it back. For example with
table.push_back(std::map<std::string, std::set<std::string>>());
Is there any way to avoid redeclaring the type, and just adding the correct typed element?
c++ c++11
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
asked Mar 25 at 6:35
VineetVineet
359411
add a comment |
When we use a complicated container in C++, like
std::vector<std::map<std::string, std::set<std::string>>> table;
The only way to add an empty map (which may represent a row or column) is to initialize a new element and push it back. For example with
table.push_back(std::map<std::string, std::set<std::string>>());
Is there any way to avoid redeclaring the type, and just adding the correct typed element?
c++ c++11
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
asked Mar 25 at 6:35
VineetVineet
359411
When we use a complicated container in C++, like
std::vector<std::map<std::string, std::set<std::string>>> table;
The only way to add an empty map (which may represent a row or column) is to initialize a new element and push it back. For example with
table.push_back(std::map<std::string, std::set<std::string>>());
Is there any way to avoid redeclaring the type, and just adding the correct typed element?
c++ c++11
c++ c++11
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
asked Mar 25 at 6:35
VineetVineet
359411
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
asked Mar 25 at 6:35
VineetVineet
359411
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
edited Mar 25 at 10:41
Mohammad Usman
21.6k134859
21.6k134859
asked Mar 25 at 6:35
VineetVineet
359411
asked Mar 25 at 6:35
VineetVineet
359411
asked Mar 25 at 6:35
VineetVineet
359411
359411
add a comment |
add a comment |
4 Answers
4
active
oldest
votes
From CLion's IntelliSense, I later found that one useful method is emplace_back(). This constructs a new object of correct type and adds it to the end of the vector.
table.emplace_back();
answered Mar 25 at 6:51
VineetVineet
359411
add a comment |
You can take advantage of copy-list-initialization (since C++11) and just write
table.push_back();
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
add a comment |
Before C++11 sometimes I use x.resize(x.size()+1), in C++11 or later you can use x.push_back().
answered Mar 25 at 6:49
65026502
88k13115218
add a comment |
Though the other answers are correct, I will add that if you couldn't take that approach, you could have benefitted from declaring some type aliases to shorten that container type name.
I can of course only guess at the logical meaning of your containers, which is another thing that this fixes!
using PhilosopherNameType = std::string;
using NeighboursType = std::set<PhilosopherNameType>;
using NeighbourMapType = std::map<PhilosopherNameType, NeighboursType>;
std::vector<NeighbourMapType> table;
table.push_back(NeighbourMapType());
I mention this because you can likely still benefit from this in other places.
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
2
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
From CLion's IntelliSense, I later found that one useful method is emplace_back(). This constructs a new object of correct type and adds it to the end of the vector.
table.emplace_back();
answered Mar 25 at 6:51
VineetVineet
359411
add a comment |
From CLion's IntelliSense, I later found that one useful method is emplace_back(). This constructs a new object of correct type and adds it to the end of the vector.
table.emplace_back();
answered Mar 25 at 6:51
VineetVineet
359411
add a comment |
From CLion's IntelliSense, I later found that one useful method is emplace_back(). This constructs a new object of correct type and adds it to the end of the vector.
table.emplace_back();
answered Mar 25 at 6:51
VineetVineet
359411
From CLion's IntelliSense, I later found that one useful method is emplace_back(). This constructs a new object of correct type and adds it to the end of the vector.
table.emplace_back();
answered Mar 25 at 6:51
VineetVineet
359411
edited Mar 25 at 7:12
answered Mar 25 at 6:51
VineetVineet
359411
answered Mar 25 at 6:51
VineetVineet
359411
answered Mar 25 at 6:51
VineetVineet
359411
359411
add a comment |
add a comment |
You can take advantage of copy-list-initialization (since C++11) and just write
table.push_back();
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
add a comment |
You can take advantage of copy-list-initialization (since C++11) and just write
table.push_back();
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
add a comment |
You can take advantage of copy-list-initialization (since C++11) and just write
table.push_back();
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
You can take advantage of copy-list-initialization (since C++11) and just write
table.push_back();
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
edited Mar 25 at 6:46
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
answered Mar 25 at 6:37
songyuanyaosongyuanyao
94.4k11182250
94.4k11182250
add a comment |
add a comment |
Before C++11 sometimes I use x.resize(x.size()+1), in C++11 or later you can use x.push_back().
answered Mar 25 at 6:49
65026502
88k13115218
add a comment |
Before C++11 sometimes I use x.resize(x.size()+1), in C++11 or later you can use x.push_back().
answered Mar 25 at 6:49
65026502
88k13115218
add a comment |
Before C++11 sometimes I use x.resize(x.size()+1), in C++11 or later you can use x.push_back().
answered Mar 25 at 6:49
65026502
88k13115218
Before C++11 sometimes I use x.resize(x.size()+1), in C++11 or later you can use x.push_back().
answered Mar 25 at 6:49
65026502
88k13115218
answered Mar 25 at 6:49
65026502
88k13115218
answered Mar 25 at 6:49
65026502
88k13115218
answered Mar 25 at 6:49
65026502
88k13115218
88k13115218
add a comment |
add a comment |
Though the other answers are correct, I will add that if you couldn't take that approach, you could have benefitted from declaring some type aliases to shorten that container type name.
I can of course only guess at the logical meaning of your containers, which is another thing that this fixes!
using PhilosopherNameType = std::string;
using NeighboursType = std::set<PhilosopherNameType>;
using NeighbourMapType = std::map<PhilosopherNameType, NeighboursType>;
std::vector<NeighbourMapType> table;
table.push_back(NeighbourMapType());
I mention this because you can likely still benefit from this in other places.
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
2
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
add a comment |
Though the other answers are correct, I will add that if you couldn't take that approach, you could have benefitted from declaring some type aliases to shorten that container type name.
I can of course only guess at the logical meaning of your containers, which is another thing that this fixes!
using PhilosopherNameType = std::string;
using NeighboursType = std::set<PhilosopherNameType>;
using NeighbourMapType = std::map<PhilosopherNameType, NeighboursType>;
std::vector<NeighbourMapType> table;
table.push_back(NeighbourMapType());
I mention this because you can likely still benefit from this in other places.
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
2
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
add a comment |
Though the other answers are correct, I will add that if you couldn't take that approach, you could have benefitted from declaring some type aliases to shorten that container type name.
I can of course only guess at the logical meaning of your containers, which is another thing that this fixes!
using PhilosopherNameType = std::string;
using NeighboursType = std::set<PhilosopherNameType>;
using NeighbourMapType = std::map<PhilosopherNameType, NeighboursType>;
std::vector<NeighbourMapType> table;
table.push_back(NeighbourMapType());
I mention this because you can likely still benefit from this in other places.
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
Though the other answers are correct, I will add that if you couldn't take that approach, you could have benefitted from declaring some type aliases to shorten that container type name.
I can of course only guess at the logical meaning of your containers, which is another thing that this fixes!
using PhilosopherNameType = std::string;
using NeighboursType = std::set<PhilosopherNameType>;
using NeighbourMapType = std::map<PhilosopherNameType, NeighboursType>;
std::vector<NeighbourMapType> table;
table.push_back(NeighbourMapType());
I mention this because you can likely still benefit from this in other places.
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
answered Mar 25 at 17:12
Lightness Races in OrbitLightness Races in Orbit
295k55479816
295k55479816
2
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
add a comment |
2
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
2
2
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
agreed. Along the same lines are the types that the STL gives you (vector::value_type iirc)
– sudo rm -rf slash
Mar 26 at 8:01
add a comment |
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