Using brace-init for a non-trivial multi-variable class
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2
I am trying to make a certain template class brace-initializable, e.g.
template<typename T>
class A {
private:
std::vector<T> _data;
std::size_t _m;
std::size_t _n;
public:
Matrix(std::size_t m, std::size_t n, const T &fill); // regular (non-trivial) constructor
Matrix(std::initializer_list<T> list);
};
However, I'm having trouble coming up with the implementation. I want to be able to do:
A<int> a = {{1, 2, 3, 4}, 2, 2};
// or something similar...e.g. C++11 style brace-init
A<int> a {{1, 2, 3, 4}, 2, 2};
I've tried:
template<typename T>
Matrix<T>::Matrix(std::initializer_list<T> list)
: _data(*list.begin()),
_m(*(list.begin() + 1)),
_n(*(list.begin() + 2)) {}
But that doesn't work for me. Help!
c++ constructor initialization initializer-list curly-braces
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
add a comment |
2
I am trying to make a certain template class brace-initializable, e.g.
template<typename T>
class A {
private:
std::vector<T> _data;
std::size_t _m;
std::size_t _n;
public:
Matrix(std::size_t m, std::size_t n, const T &fill); // regular (non-trivial) constructor
Matrix(std::initializer_list<T> list);
};
However, I'm having trouble coming up with the implementation. I want to be able to do:
A<int> a = {{1, 2, 3, 4}, 2, 2};
// or something similar...e.g. C++11 style brace-init
A<int> a {{1, 2, 3, 4}, 2, 2};
I've tried:
template<typename T>
Matrix<T>::Matrix(std::initializer_list<T> list)
: _data(*list.begin()),
_m(*(list.begin() + 1)),
_n(*(list.begin() + 2)) {}
But that doesn't work for me. Help!
c++ constructor initialization initializer-list curly-braces
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n);
– Piotr Skotnicki
Nov 17 '18 at 1:10
add a comment |
2
2
2
I am trying to make a certain template class brace-initializable, e.g.
template<typename T>
class A {
private:
std::vector<T> _data;
std::size_t _m;
std::size_t _n;
public:
Matrix(std::size_t m, std::size_t n, const T &fill); // regular (non-trivial) constructor
Matrix(std::initializer_list<T> list);
};
However, I'm having trouble coming up with the implementation. I want to be able to do:
A<int> a = {{1, 2, 3, 4}, 2, 2};
// or something similar...e.g. C++11 style brace-init
A<int> a {{1, 2, 3, 4}, 2, 2};
I've tried:
template<typename T>
Matrix<T>::Matrix(std::initializer_list<T> list)
: _data(*list.begin()),
_m(*(list.begin() + 1)),
_n(*(list.begin() + 2)) {}
But that doesn't work for me. Help!
c++ constructor initialization initializer-list curly-braces
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
I am trying to make a certain template class brace-initializable, e.g.
template<typename T>
class A {
private:
std::vector<T> _data;
std::size_t _m;
std::size_t _n;
public:
Matrix(std::size_t m, std::size_t n, const T &fill); // regular (non-trivial) constructor
Matrix(std::initializer_list<T> list);
};
However, I'm having trouble coming up with the implementation. I want to be able to do:
A<int> a = {{1, 2, 3, 4}, 2, 2};
// or something similar...e.g. C++11 style brace-init
A<int> a {{1, 2, 3, 4}, 2, 2};
I've tried:
template<typename T>
Matrix<T>::Matrix(std::initializer_list<T> list)
: _data(*list.begin()),
_m(*(list.begin() + 1)),
_n(*(list.begin() + 2)) {}
But that doesn't work for me. Help!
c++ constructor initialization initializer-list curly-braces
c++ constructor initialization initializer-list curly-braces
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
asked Nov 17 '18 at 1:01
Jonathan LeeJonathan Lee
707
707
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n);
– Piotr Skotnicki
Nov 17 '18 at 1:10
add a comment |
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n);
– Piotr Skotnicki
Nov 17 '18 at 1:10
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n);– Piotr Skotnicki
Nov 17 '18 at 1:10
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n);– Piotr Skotnicki
Nov 17 '18 at 1:10
add a comment |
1 Answer
1
active
oldest
votes
3
In order to convert from an initializer_list to a vector you may copy all the elements.
STL makes this pretty nice with the begin/end iterators. Here's all the possible constructors for vector
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n)
: _data(list.begin(), list.end()) // This is what might help
, _m(m)
,_n(n)
{
}
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
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
3
In order to convert from an initializer_list to a vector you may copy all the elements.
STL makes this pretty nice with the begin/end iterators. Here's all the possible constructors for vector
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n)
: _data(list.begin(), list.end()) // This is what might help
, _m(m)
,_n(n)
{
}
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
add a comment |
3
In order to convert from an initializer_list to a vector you may copy all the elements.
STL makes this pretty nice with the begin/end iterators. Here's all the possible constructors for vector
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n)
: _data(list.begin(), list.end()) // This is what might help
, _m(m)
,_n(n)
{
}
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
add a comment |
3
3
3
In order to convert from an initializer_list to a vector you may copy all the elements.
STL makes this pretty nice with the begin/end iterators. Here's all the possible constructors for vector
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n)
: _data(list.begin(), list.end()) // This is what might help
, _m(m)
,_n(n)
{
}
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
In order to convert from an initializer_list to a vector you may copy all the elements.
STL makes this pretty nice with the begin/end iterators. Here's all the possible constructors for vector
Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n)
: _data(list.begin(), list.end()) // This is what might help
, _m(m)
,_n(n)
{
}
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
answered Nov 17 '18 at 1:12
Chris McChris Mc
32225
32225
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
add a comment |
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
Wow, you are a genius. Never thought that you could have extra parameters after the list. I don't know why; it makes perfect sense. Thanks!
– Jonathan Lee
Nov 17 '18 at 1:20
add a comment |
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Matrix(std::initializer_list<T> list, std::size_t m, std::size_t n);– Piotr Skotnicki
Nov 17 '18 at 1:10