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Declaring 2 (or even multi-) dimensional std::arrays elegantly
How do I use arrays in C++?Why is reading lines from stdin much slower in C++ than Python?Image Processing: Algorithm Improvement for 'Coca-Cola Can' RecognitionHow to avoid “if” chains?Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviationsstd::array and bytes readingSort 2 dimensional c array with std::sort
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I'm using 2-dimensional arrays based on std::array.
Basically instead of:
MyType myarray[X_SIZE][Y_SIZE];
I have:
std::array<std::array<MyType, Y_SIZE>, X_SIZE> myarray;
This works perfectly fine but IMO the declaration it is not very readable.
Is there a way to declare this using some clever C++ template mecanism, so the declaration could look something like this?
My2DArray<Mytype, X_SIZE, Y_SIZE> myarray;
c++ stdarray
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
add a comment |
I'm using 2-dimensional arrays based on std::array.
Basically instead of:
MyType myarray[X_SIZE][Y_SIZE];
I have:
std::array<std::array<MyType, Y_SIZE>, X_SIZE> myarray;
This works perfectly fine but IMO the declaration it is not very readable.
Is there a way to declare this using some clever C++ template mecanism, so the declaration could look something like this?
My2DArray<Mytype, X_SIZE, Y_SIZE> myarray;
c++ stdarray
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
1
I don't think code elegance was/is a priority of 'Modern' C++!
– Adrian
10 hours ago
I would expect it to be[Y][X](andstd::array<std::array<T, X>, Y>in the template in the answer), as usually I think about X being the base dimension, which is iterated mostly continuously.. (of course if you iterate mostly through Y, then your example is optimal too, so it depends on the usage)
– Ped7g
10 hours ago
@Ped7g no, X,Y rather than Y,X is on purpose because accessing is done like this:myarray[x_index][y_index].
– Jabberwocky
9 hours ago
@Jabberwocky that's what I am talking about, if it's for exampleint map[4][3];then the memory layout is[0][0], [0][1], [0][2], [1][0], [1][1], ..., i.e. the second dimension form continuous blocks of integers, so you should (when possible) iterate over second dimension in the inner loop, and first dimension in the outer loop. In your dimension that means to have X as outer loop and Y inner (I mean for cases where this distinction is even possible, like adding of matrices, in multiplying it doesn't matter that much, as one of the two matrices has to be traversed in suboptimal order), etc
– Ped7g
9 hours ago
@Ped7g it's not about optimisation here but solely about code readability. But you are right.
– Jabberwocky
9 hours ago
add a comment |
I'm using 2-dimensional arrays based on std::array.
Basically instead of:
MyType myarray[X_SIZE][Y_SIZE];
I have:
std::array<std::array<MyType, Y_SIZE>, X_SIZE> myarray;
This works perfectly fine but IMO the declaration it is not very readable.
Is there a way to declare this using some clever C++ template mecanism, so the declaration could look something like this?
My2DArray<Mytype, X_SIZE, Y_SIZE> myarray;
c++ stdarray
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
I'm using 2-dimensional arrays based on std::array.
Basically instead of:
MyType myarray[X_SIZE][Y_SIZE];
I have:
std::array<std::array<MyType, Y_SIZE>, X_SIZE> myarray;
This works perfectly fine but IMO the declaration it is not very readable.
Is there a way to declare this using some clever C++ template mecanism, so the declaration could look something like this?
My2DArray<Mytype, X_SIZE, Y_SIZE> myarray;
c++ stdarray
c++ stdarray
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
asked 10 hours ago
JabberwockyJabberwocky
29.8k10 gold badges43 silver badges78 bronze badges
29.8k10 gold badges43 silver badges78 bronze badges
1
I don't think code elegance was/is a priority of 'Modern' C++!
– Adrian
10 hours ago
I would expect it to be[Y][X](andstd::array<std::array<T, X>, Y>in the template in the answer), as usually I think about X being the base dimension, which is iterated mostly continuously.. (of course if you iterate mostly through Y, then your example is optimal too, so it depends on the usage)
– Ped7g
10 hours ago
@Ped7g no, X,Y rather than Y,X is on purpose because accessing is done like this:myarray[x_index][y_index].
– Jabberwocky
9 hours ago
@Jabberwocky that's what I am talking about, if it's for exampleint map[4][3];then the memory layout is[0][0], [0][1], [0][2], [1][0], [1][1], ..., i.e. the second dimension form continuous blocks of integers, so you should (when possible) iterate over second dimension in the inner loop, and first dimension in the outer loop. In your dimension that means to have X as outer loop and Y inner (I mean for cases where this distinction is even possible, like adding of matrices, in multiplying it doesn't matter that much, as one of the two matrices has to be traversed in suboptimal order), etc
– Ped7g
9 hours ago
@Ped7g it's not about optimisation here but solely about code readability. But you are right.
– Jabberwocky
9 hours ago
add a comment |
1
I don't think code elegance was/is a priority of 'Modern' C++!
– Adrian
10 hours ago
I would expect it to be[Y][X](andstd::array<std::array<T, X>, Y>in the template in the answer), as usually I think about X being the base dimension, which is iterated mostly continuously.. (of course if you iterate mostly through Y, then your example is optimal too, so it depends on the usage)
– Ped7g
10 hours ago
@Ped7g no, X,Y rather than Y,X is on purpose because accessing is done like this:myarray[x_index][y_index].
– Jabberwocky
9 hours ago
@Jabberwocky that's what I am talking about, if it's for exampleint map[4][3];then the memory layout is[0][0], [0][1], [0][2], [1][0], [1][1], ..., i.e. the second dimension form continuous blocks of integers, so you should (when possible) iterate over second dimension in the inner loop, and first dimension in the outer loop. In your dimension that means to have X as outer loop and Y inner (I mean for cases where this distinction is even possible, like adding of matrices, in multiplying it doesn't matter that much, as one of the two matrices has to be traversed in suboptimal order), etc
– Ped7g
9 hours ago
@Ped7g it's not about optimisation here but solely about code readability. But you are right.
– Jabberwocky
9 hours ago
1
1
I don't think code elegance was/is a priority of 'Modern' C++!
– Adrian
10 hours ago
I don't think code elegance was/is a priority of 'Modern' C++!
– Adrian
10 hours ago
I would expect it to be
[Y][X] (and std::array<std::array<T, X>, Y> in the template in the answer), as usually I think about X being the base dimension, which is iterated mostly continuously.. (of course if you iterate mostly through Y, then your example is optimal too, so it depends on the usage)– Ped7g
10 hours ago
I would expect it to be
[Y][X] (and std::array<std::array<T, X>, Y> in the template in the answer), as usually I think about X being the base dimension, which is iterated mostly continuously.. (of course if you iterate mostly through Y, then your example is optimal too, so it depends on the usage)– Ped7g
10 hours ago
@Ped7g no, X,Y rather than Y,X is on purpose because accessing is done like this:
myarray[x_index][y_index].– Jabberwocky
9 hours ago
@Ped7g no, X,Y rather than Y,X is on purpose because accessing is done like this:
myarray[x_index][y_index].– Jabberwocky
9 hours ago
@Jabberwocky that's what I am talking about, if it's for example
int map[4][3]; then the memory layout is [0][0], [0][1], [0][2], [1][0], [1][1], ..., i.e. the second dimension form continuous blocks of integers, so you should (when possible) iterate over second dimension in the inner loop, and first dimension in the outer loop. In your dimension that means to have X as outer loop and Y inner (I mean for cases where this distinction is even possible, like adding of matrices, in multiplying it doesn't matter that much, as one of the two matrices has to be traversed in suboptimal order), etc– Ped7g
9 hours ago
@Jabberwocky that's what I am talking about, if it's for example
int map[4][3]; then the memory layout is [0][0], [0][1], [0][2], [1][0], [1][1], ..., i.e. the second dimension form continuous blocks of integers, so you should (when possible) iterate over second dimension in the inner loop, and first dimension in the outer loop. In your dimension that means to have X as outer loop and Y inner (I mean for cases where this distinction is even possible, like adding of matrices, in multiplying it doesn't matter that much, as one of the two matrices has to be traversed in suboptimal order), etc– Ped7g
9 hours ago
@Ped7g it's not about optimisation here but solely about code readability. But you are right.
– Jabberwocky
9 hours ago
@Ped7g it's not about optimisation here but solely about code readability. But you are right.
– Jabberwocky
9 hours ago
add a comment |
1 Answer
1
active
oldest
votes
If you want just 2D arrays, it's fairly straightforward:
template <class T, std::size_t X, std::size_t Y>
using My2DArray = std::array<std::array<T, Y>, X>;
If you want a generic mechanism not limited to 2D arrays, it can be done too:
template <class T, std::size_t N, std::size_t... Ns>
struct AddArray
using type = std::array<typename AddArray<T, Ns...>::type, N>;
;
template <class T, std::size_t N>
struct AddArray<T, N>
using type = std::array<T, N>;
;
template <class T, std::size_t... N>
using MyNDArray = typename AddArray<T, N...>::type;
[Live example]
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
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
If you want just 2D arrays, it's fairly straightforward:
template <class T, std::size_t X, std::size_t Y>
using My2DArray = std::array<std::array<T, Y>, X>;
If you want a generic mechanism not limited to 2D arrays, it can be done too:
template <class T, std::size_t N, std::size_t... Ns>
struct AddArray
using type = std::array<typename AddArray<T, Ns...>::type, N>;
;
template <class T, std::size_t N>
struct AddArray<T, N>
using type = std::array<T, N>;
;
template <class T, std::size_t... N>
using MyNDArray = typename AddArray<T, N...>::type;
[Live example]
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
add a comment |
If you want just 2D arrays, it's fairly straightforward:
template <class T, std::size_t X, std::size_t Y>
using My2DArray = std::array<std::array<T, Y>, X>;
If you want a generic mechanism not limited to 2D arrays, it can be done too:
template <class T, std::size_t N, std::size_t... Ns>
struct AddArray
using type = std::array<typename AddArray<T, Ns...>::type, N>;
;
template <class T, std::size_t N>
struct AddArray<T, N>
using type = std::array<T, N>;
;
template <class T, std::size_t... N>
using MyNDArray = typename AddArray<T, N...>::type;
[Live example]
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
add a comment |
If you want just 2D arrays, it's fairly straightforward:
template <class T, std::size_t X, std::size_t Y>
using My2DArray = std::array<std::array<T, Y>, X>;
If you want a generic mechanism not limited to 2D arrays, it can be done too:
template <class T, std::size_t N, std::size_t... Ns>
struct AddArray
using type = std::array<typename AddArray<T, Ns...>::type, N>;
;
template <class T, std::size_t N>
struct AddArray<T, N>
using type = std::array<T, N>;
;
template <class T, std::size_t... N>
using MyNDArray = typename AddArray<T, N...>::type;
[Live example]
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
If you want just 2D arrays, it's fairly straightforward:
template <class T, std::size_t X, std::size_t Y>
using My2DArray = std::array<std::array<T, Y>, X>;
If you want a generic mechanism not limited to 2D arrays, it can be done too:
template <class T, std::size_t N, std::size_t... Ns>
struct AddArray
using type = std::array<typename AddArray<T, Ns...>::type, N>;
;
template <class T, std::size_t N>
struct AddArray<T, N>
using type = std::array<T, N>;
;
template <class T, std::size_t... N>
using MyNDArray = typename AddArray<T, N...>::type;
[Live example]
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
edited 9 hours ago
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
answered 10 hours ago
AngewAngew
142k13 gold badges284 silver badges372 bronze badges
142k13 gold badges284 silver badges372 bronze badges
add a comment |
add a comment |
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1
I don't think code elegance was/is a priority of 'Modern' C++!
– Adrian
10 hours ago
I would expect it to be
[Y][X](andstd::array<std::array<T, X>, Y>in the template in the answer), as usually I think about X being the base dimension, which is iterated mostly continuously.. (of course if you iterate mostly through Y, then your example is optimal too, so it depends on the usage)– Ped7g
10 hours ago
@Ped7g no, X,Y rather than Y,X is on purpose because accessing is done like this:
myarray[x_index][y_index].– Jabberwocky
9 hours ago
@Jabberwocky that's what I am talking about, if it's for example
int map[4][3];then the memory layout is[0][0], [0][1], [0][2], [1][0], [1][1], ..., i.e. the second dimension form continuous blocks of integers, so you should (when possible) iterate over second dimension in the inner loop, and first dimension in the outer loop. In your dimension that means to have X as outer loop and Y inner (I mean for cases where this distinction is even possible, like adding of matrices, in multiplying it doesn't matter that much, as one of the two matrices has to be traversed in suboptimal order), etc– Ped7g
9 hours ago
@Ped7g it's not about optimisation here but solely about code readability. But you are right.
– Jabberwocky
9 hours ago